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					A structure is not truly solved until it is refined! :
tricks and hints for using Alan Larson and Bob
von Dreele's GSAS, and Brian Toby's
EXPGUI, for combined X-ray / Neutron
refinement and restrained Rietveld refinement of
large polymeric inorganics and minerals.

                Lachlan M. D. Cranswick,
                CCP14 (Collaborative Computation Project No 14 for
                Single Crystal and Powder Diffraction)
                Department of Crystallography;
                Birkbeck College, University of London,
                Malet Street, Bloomsbury, London, WC1E 7HX, UK.
                E-mail: l.m.d.cranswick@dl.ac.uk
                WWW: http://www.ccp14.ac.uk
    Notes Free Zone - they are on the web
http://www.ccp14.ac.uk/poster-talks/agu2002b/




      Slide 2             AGU 2002: “hints and tricks for using GSAS Rietveld”
                Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                             Talk Aims
• Provide hints on performing restrained Rietveld
  refinement of large inorganics using GSAS
  including:

   –   Data conversion
   –   Histogram weighting
   –   Charge Balance Restraints
   –   Total cell composition restraints
   –   Bond length restraints
   –   Bond angle restraints
   –   Using Platon and WinGX to help validate the structure

       Slide 3             AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                Topics Discussed
• Converting Madsen and Hill VCT data and
  x,y,weight column data into GSAS format
• Using Brian Toby’s EXPGUI as a primary
  interface into GSAS
• Hints on using GSAS for combined X-ray /
  Neutron refinement
• Hints on GSAS Rietveld for restrained
  refinement of large inorganic polymeric
  framework structrures
• Using macros in GSAS

    Slide 4             AGU 2002: “hints and tricks for using GSAS Rietveld”
              Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
 An initial point - computer skills
• When doing complicated (and not so
  complicated crystallography and powder
  diffraction), it is assumed the user has good
  general computer skills.
   – General program installation and configuration
   – Good text editing skills
   – Having multiple programs open and interacting
     between them
   – Cut and paste using both mouse and keyboard speed
     keys.


    Slide 5             AGU 2002: “hints and tricks for using GSAS Rietveld”
              Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                                GSAS
• by Bob von Dreele and Alan
  Larsen - ftp://ftp.lanl.gov/public/gsas/
• CCP14 based resources:
   – http://www.ccp14.ac.uk/solution/gsas/

• What may look like minor
  changes can result in ability to
  handle what were intractable
  problems.




             Slide 6             AGU 2002: “hints and tricks for using GSAS Rietveld”
                       Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
       GSAS: Some Relevant Background
• by Bob von Dreele and                          • Restraints
  Alan Larsen                                          – Bond angle
• Menu based control                                   – Bond length
                                                       – Planar
• Available for Windows /
                                                       – Total Chemistry / charge
  DOS / Linux / SGI                                      balance
• Separate GUI by Brian                                – Chiral volume
  Toby (EXPGUI)                                        – Phi/psi group
                                                       – Torsion angle
• Combined X-ray /
                                                 • Manual Marquadt damping
  Neutron / Single Crystal /
                                                 • Atom shift limits
  Powder Diffraction
                                                 • Lots of other features
• Integrated Fourier map
  generation and viewing

     Slide 7             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
              Brian Toby’s EXPGUI Interface for GSAS
User friendlier to start using GSAS via EXPGUI
(A new combined installer makes it very easy to start using GSAS.)
http://www.ncnr.nist.gov/programs/crystallography/software/expgui/expgui_intro.html




              Slide 8              AGU 2002: “hints and tricks for using GSAS Rietveld”
                         Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                       (1 of 13)

  • Run EXPGUI and go to the required directory and
    enter a new filename (in this case pbso4) and press
    “read”. When prompted, then press the “Create” icon




        Slide 9             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (2 of 13)

  • When prompted, enter an experimental title then press
    the “Set” icon.




        Slide 10             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (3 of 13)

  • Click on the “Phase” tab and then the “Add Phase”
    Icon. Input the cell and spacegroup information




        Slide 11             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (4 of 13)

  • Click “Add” then “Continue” to the cell and
    spacegroup information to be incorporated into GSAS.




        Slide 12             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (5 of 13)

  • Click “Add New Atoms” and add in the starting model
    either by hand or importing a PowderCell format file.




        Slide 13             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (6 of 13)

  • Click “Add Atoms” to get the starting model into
    GSAS




        Slide 14             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (7 of 13)

  • Set appropriate damping factors (I tend to like somewhere
    between 7 and 9)
  • (Lessen damping factors if parameter shifts are too small)




        Slide 15             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (8 of 13)

  • Add the first XRD diffraction file: Select “Histogram”
    tab then “Add New Histogram” icon.




        Slide 16             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                        (9 of 13)

  • Via the GUI, select the data file and the instrument
    parameter file. (in this case an XRD data file)




        Slide 17             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                          (10 of 13)

   • Click “Add” to add the XRD file into GSAS. Change the damping
     factors and fix up any incorrect diffractometer constants (I.e., the
     parameter file may have incorrect information in it)




           Slide 18             AGU 2002: “hints and tricks for using GSAS Rietveld”
                      Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement                                         (11 of 13)

   • It is easy to add another data file. Select the “Add New
     Histogram” icon. (select the Bank number if this is relevant)




          Slide 19             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement (12 of 13)
  • Click “Add” to add the second XRD file into GSAS. Again, change
    the damping factors and fix up any incorrect diffractometer constants
    (I.e., the parameter file may have incorrect information in it)




          Slide 20             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Easy to start a new refinement (13 of 13)

 • Now you are ready to run Powpref and
   Genles and start refining the various
   “relevant” parameters
 • Under Profile, Powder XRD data might be happier
   being fitted with a type 3 profile function:
    –   pseudo-Voight with Finger Cox Jephcoat peak asymmetry correction

 • One extra hint for Bragg-Brentano XRD users -
   sample displacement parameter is “shft” in the
   profile options (can be preferable to use this instead of “zero
   offset”)

          Slide 21             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Profile Screen in EXPGUI with shft




       Slide 22             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
New(ish) Features in Brian Toby’s EXPGUI
• Graphically define the background
• Graphically exclude regions
• Can export structures to Platon format
  (Addsym, etc)




     Slide 23             AGU 2002: “hints and tricks for using GSAS Rietveld”
                Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Graphically Defining the Background (1 of 3)

   • After powpref, select “powder, bkgedit” and use point
     and click with the mouse to select background points




         Slide 24             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Graphically Defining the Background (2 of 3)

   • Use the Fit icon to fit a Chebyshev function through
     the data points - increase number of terms as required




         Slide 25             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Graphically Defining the Background (3 of 3)

   • Save into EXP file. Background is now fixed but can
     be refined at the click of a button. Done.




         Slide 26             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Graphically Excluding Regions (1 of 3)

• After powpref “and” genles (0 cycles just to perform a
  “calculation”), select “powder, excledt”




      Slide 27             AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Graphically Excluding Regions (2 of 3)

• Point and click to select excluded regions




      Slide 28             AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: Graphically Excluding Regions (3 of 3)

• Run powpref and genles for this to take effect




      Slide 29             AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Brian Toby’s EXPGUI: If things go beserk: Backtracking through
        previous runs to when before things went beserk.
• Select “File, Open” and the “Include Archived Files”




       Slide 30             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
             GSAS and example ceramic /
             polymeric inorganic problem
In this example, a perovskite
based ceramic relevant to the
                                                             – 54 possible “split
wireless communications and                                    occupancy” framework
the mobile phone industry                                      metal sites
(High Q ferroelectric)                                       – 54 possible atom / vacancy
                                                               interstitial sites
 –>120 atoms in R3                                           – 162 oxygen sites
                                                             – >1600 bond restraints
 –>320 atoms in C1                                           – >200 atom constraints
                                                             – >150 atoms linked within a
                                                               single constraint


      Slide 31             AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                        GSAS and example ceramic / polymeric
                       inorganic problem: chronic peak overlap

• Structure is Pseudo
  Cubic
   – a=b=c= 23.9 Å
   – Chronic peak overlap
   – No non-overlapping
     reflections
• Screen image from
  EXPGUI shows some
  HKLs matching to
  some “LOW ANGLE”
  peaks.
   – Shift Left mouse button
     in Expgui’s Liveplot

            Slide 32              AGU 2002: “hints and tricks for using GSAS Rietveld”
                        Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
    Will be concentrating on HOW to using
         GSAS for this type of problem
• Often hear that a program can handle a problem.
• But often is not obvious or obscure how to go about
  using a program.
• This will be concentrating on the “HOW”.
• Structure is presently unpublished and only 99.9%
  finished
• Ian Grey of CSIRO Australia or Bob Roth of NIST
  USA would be more appropriate to talk about the
  crystal chemistry and the structure itself.


       Slide 33             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
  Nuances and People Involved in this structure
• Lead by Ian Grey (CSIRO, Melbourne Australia) and Bob Roth (NIST, Gaithersburg, USA)
• Synthesis: Bob Roth and Julia Chan (NIST, Gaithersburg) (is ~3 months of work and furnace time to
  synthesize a decent size batch of sample)
• TEM: Igor Levin (NIST, Gaithersburg) (looks like microdomain twinning problems)
• Single Crystal Work: Gus Mumme and Ian Grey (CSIRO, Melbourne) (looks like microdomain
  twinning problems)
• Powder Indexing / Le Bail fitting for looking at cell and spacegroup: Lachlan Cranswick
  (done at Columbia University) (Crysfire/Chekcell/Rietica)
• Structure Solution: Ian Grey and Gus Mumme (CSIRO, Melbourne)
    –     Atom Ordering: Gus Mumme and Ian Grey (CSIRO, Melbourne)
    –     Tilt Model: Ian Grey and Gus Mumme (CSIRO, Melbourne)
    –     Basic structure from chemical crystallographic arguments
    –     Starting atom ordering model from Shelxl and CSRIET structure refinement
    – (Complex tilt model obtained from refining the perovskite subcell and
      looking at the Fourier difference map for peaks giving an indication of tilt
      directions and magnitudes)
• GSAS Structure Refinement: Lachlan Cranswick (done at Columbia University)
• New single crystal work based on GSAS Refined structure: Ian Grey and Pierre Bordet


              Slide 34                AGU 2002: “hints and tricks for using GSAS Rietveld”
                            Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
       Is GSAS the only effective program for large
      restrained inorganic Rietveld Refinements(?)
• Ability to handle very large arrays not the only issue
• Controllable - via a menu / scripting system amenable
  to scripting and automation
• Large variety of restraints
• Restraints can be disabled but still used for diagnostic
  purposes
• Can easily disable/enable restraints and histograms
  (cyclic refinement instead of combined X-ray / Neutron
  refinement)


        Slide 35             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS : YES! - at present the only effective
  Rietveld system for these types of large problems
• GSAS (by the Anna                               • Other Rietveld Programs
  Karenina principle - a                            affected by one or more of the
                                                    following problems
  happy family):
                                                  •    Cannot handle large numbers of
• Can handle large numbers of                          atoms or restraints
  atoms and restraints                            •    Don’t have many types of restraints
• Large variety of restraints                     •    Manual editing of ASCII files or
                                                       GUIs that do not easily allow quick
• Menu based control amenable                          changes to large numbers of atoms
  to scripts and automation                       •    Problematic enabling and disabling
• Easy enabling and disable of                         of restrains and histograms
  histograms                                      •    No integrated Fourier map
                                                       generation and viewing
• Integrated Fourier map
                                                  •    Can only handle constant
  including peak search                                wavelength neutron and angular
• TOF Neutron / EDX as well                            dispersive X-ray diffraction data.

     Slide 36             AGU 2002: “hints and tricks for using GSAS Rietveld”
                Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
   GSAS - relevant newish features

• Weighting of individual histograms /
  powder patterns
• Larger arrays for atom constraints
• Larger arrays for total chemistry constraints
• Viewing of larger Fourier electron density
  contour maps
• Other misc. changes


   Slide 37             AGU 2002: “hints and tricks for using GSAS Rietveld”
              Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
       GSAS scales up!: to the point of refining protein data

•   As cited in R. B. Von Dreele, P.
    W. Stephens, G. D. Smith and
    R. H. Blessing, "The first
    protein crystal structure
    determined from high-
    resolution X-ray powder
    diffraction data: a variant of
    T3R3 human insulin-zinc
    complex produced by
    grinding", Acta Cryst. (2000).
    D56, 1549-1553.




    http://journals.iucr.org/d/issues/2000/12/00/issconts.html
            Slide 38             AGU 2002: “hints and tricks for using GSAS Rietveld”
                       Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: Individual Histogram Weighting
• You don’t
  always have a
  choice on data
  collection
• Thus may need
  to weight
  histograms
  (diffraction data)
  such that they
  are roughly of
  equal weighting

         Slide 39             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
        GSAS: Individual Histogram Weighting
• In this
  example, you
  need to zoom
  up a bit.
  – XRD pattern is
    ~1500 times
    more intense than
    the
    corresponding
    neutron pattern
  – Problematic for
    combined
    refinement and
    setting restraints

        Slide 40             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: Individual Histogram Weighting
• Set via EXPEDT (using Sum(w*d**2) as a guide)
• (changing weight on
  Histogram 1 - XRD)
   –   y !backup
   –   p !powder prep
   –   h !histograms
   –   f 1 !weighting on hist 1
   –   .001 !set the weighting
   –   x x x !exit menus
   –   x !exit expedt
• Run Powpref for new
  weighting to take effect
          Slide 41             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
   GSAS: If you DON’T Use Histogram Weighting
X-ray 8.0% R(F**2)                             Neutron 28.1% R(F**2)




    Slide 42             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
         GSAS: If you DO Use Histogram Weighting
X-ray 8.3% R(F**2)                             Neutron 11.7% R(F**2)




    Slide 43             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                    GSAS: Atom shift limits
(so that atoms cannot shift more than a define absolute amount (Å))


• Set via EXPEDT
  – y !backup
  – l !least squares setup
  – l !least squares controls
  – a !atom shift limits
  – 0.1 !set the max allowed
    atom shift (0.1 Å in this
    example)
  – x x x !exit menus
  – x !exit expedt

        Slide 44             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
      GSAS: Rod Hill and Ian Madsen VCT data collection

• If you do have a
  choice of data
  collection
  strategies for XRD
  - use variable
  count time (VCT)
•   Commercial vendors
    partially to blame for only
    having obsolescent data
    collection options in their
    data logging software.
•   Still may need to play with
    weighting of histograms
    for “fine” control of the
    combined refinement.              VCT Fortran Source Code with references is available:
                       http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/csirominerals-anon-ftp/pub/xtallography/


            Slide 45             AGU 2002: “hints and tricks for using GSAS Rietveld”
                       Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
           VCT for Refinement (1 of 4)
Variable Count Time data (as collected - CAD4 style)




    Slide 46             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                  VCT for Refinement (2 of 4)
Variable Count Time data (normalised as FCT)




     Slide 47             AGU 2002: “hints and tricks for using GSAS Rietveld”
                Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                  VCT for Refinement (3 of 4)
Variable Count Time data (normalised as FCT)




     Slide 48             AGU 2002: “hints and tricks for using GSAS Rietveld”
                Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                 VCT for Refinement (4 of 4)
Variable Count Time data (displayed as VCT)




    Slide 49             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Getting Madsen and Hill VCT data into GSAS ESD format

• Mark Bowden’s VCTCONV for DOS (runs on Windows)
  – Download: http://www.ceramics.irl.cri.nz/Convert.htm




       Slide 50             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
 Getting ASCII x,y,weight data into GSAS ESD format
• Using Nita Dragoe’s Powder v4 for Windows
  – (sequel to “Convert for Windows”)
  – Download via: http://www.ccp14.ac.uk/tutorial/powder/
     • Open the x,y,z “free ascii” data
     • Save as GSAS CW ESD format
     • Done!




       Slide 51             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
  Setting up a Restrained Rietveld refinement of > 300 atom
                    polymeric inorganic structures in GSAS

• Initial problem is setting everything up and the
  control of the refinement.
• But need the flexibility to change as you may only
  find new information while refining the structure.
  (change of spacegroup being the most obvious)
   – Eric Dowty’s shareware Cryscon can be very quick and effective for
     transforming structures from one cell and spacegroup to another.
     http://www.shapesoftware.com/#anchor_cryscon

• One solution is to use a spreadsheet program that
  allows for flexibility and extendability (MS-EXCEL
  for Windows)


     Slide 52             AGU 2002: “hints and tricks for using GSAS Rietveld”
                Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
Restrained refinement in GSAS: setting up an EXCEL spreadsheet
• CCP14 based tutorial and example files at :
  http://www.ccp14.ac.uk/solution/gsas/restrained_inorganic.html

• Create GSAS script commands in EXCEL and save into txt MACRO files
  for importing into GSAS.
   – (if applicable - model in arbitrary co-ordinates)
   – Structure co-ordinates (if applicable - generated from previous model)
   – Crystals (Watkin, Cooper, et al) structure co-ordinates for generating
       bond restraint lists for conversion by Scott Belmonte’s “coue” software
       into GSAS macro format.
         • Crystals: http://www.xtl.ox.ac.uk/
         • Coue: http://www.ccp14.ac.uk/ccp/web-mirrors/scott-belmonte-software/
   – Atom constraints
   – Total cell contents and/or charge balance constraints
   – If applicable, other scripts for controlling GSAS


          Slide 53             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                           GSAS: setting up an EXCEL spreadsheet:
                                        Example Atom Co-ordinates
• Calculate or import an atom
  list within Excel where it can
  be easily manipulated.

• In GSAS, you input the atom
  list via EXPEDT
   – kla

• Use Windows “cut and paste”
  or @r (import macro file
  command) while in the
  relevant menu


        Slide 54             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
             GSAS: setting up an EXCEL spreadsheet:
          ConTEXT freeware text editor and column editing
• The freeware ConTEXT editor
  can be very effective in getting
  bits of structure (or extracting
  HKL files) from text files using
  it’s “column editing” ability.
   – http://www.fixedsys.com/context/


• The column editor function is
  not on the menu but is called
  using [CONTROL] L. (cannot
  use the mouse for click and
  drag while in column editing
  mode - only the keyboard and
  arrow keys)
         Slide 55             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                                   GSAS: setting up an EXCEL spreadsheet:
              Input for Crystals to generate GSAS bond restraints lists

• Just use EXCEL “=“
  commands to copy over
  values from GSAS atom list
• Got to keep the atom numbers
  the same as GSAS atoms
  controls are based on the atom
  numbers
• Inputting bond length
  restraints in EXPEDT:
   – klsd

• More details given at:
http://www.ccp14.ac.uk/solution/gsas/restrained
     _inorganic.html



             Slide 56                AGU 2002: “hints and tricks for using GSAS Rietveld”
                           Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                GSAS: setting up an EXCEL spreadsheet:
      Dual Occupancy Atom Constraints (in expedt: k l a k)

• Just copy and paste to
  extend the atom constraints
  to the desired number of
  atom sites. In this example
  for 108 atoms which would
  be painful to set up
  manually in GSAS.




       Slide 57             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                      GSAS: setting up an EXCEL spreadsheet:
                Total Cell Content Restraints (in expedt: k l s c)

• Extend as required
  depending on the number
  of atoms you wish to link
  into the constraint.

• The total number of atoms
  on the defined sites in this
  example is restrained to 81




     Slide 58              AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                      GSAS: setting up an EXCEL spreadsheet:
                   Charge Balance Restraints (in expedt: k l s c)
• Just use the Total Cell Contents
  Restraint which does not care what
  the value physically represent.
• To enforce charge balance just put
  the ionization value of each atom
  site - which should sum to zero.
• Simple example in the screen
  dump.
• The Total Chemistry Restraint will
  performs the sum calculation for
  you and tell you what the present
  sum is in the restraints menu.
• Even if you don’t use the restraint,
  inputting this can be a useful, quick
  check that you have charge balance.


       Slide 59             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
      GSAS: importing all these macro files into GSAS

• Copy the Excel cells to a TXT file.
• Use an Editor such as PFE to replace all “TABS” with “spaces”:
   – http://www.ccp14.ac.uk/ccp/web-mirrors/pfe/people/cpaap/pfe/



• Use the @r - import
  macro file command
  while in the relevant
  menu


• Done!

         Slide 60             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
GSAS: turning off /on histograms, restraints, atoms in EXPGUI
  • Histograms can be turned on and off in Brian Toby’s EXPGUI via the
    “histogram” menu using “Set Histogram Use Flags” Icon.




        Slide 61             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
GSAS: turning off /on histograms, restraints, atoms in EXPEDT
  • Also can be done in GSAS’s EXPEDT
     – kls
     – u - The use command

  • e.g., turn off X-ray data (histogram 1), turn on bond restraints (histogram
    2) and neutron data (histogram 3)
         kls        ! Go into EXPEDT restraints menu
         u1         ! Use histogram 1 - X-ray Data
         n          ! No
         u2         ! Use histogram 2 - Bond Restraints
         y          ! Yes
         u3         ! Use histogram 3 - Neutron Data
         y          ! Yes
         xxx        ! Exit EXPEDIT menus and quit


        Slide 62             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                          GSAS: using restraints as diagnostics
•   Restraints don’t have to be enabled to exist inside GSAS
•   Restraints can also be used diagnostically even if they are not enabled
•   E.g., Charge Balance :
•   Following screen dumps shows that the occupancies of the various metals
    are such that the total cell is out of charge balance.
     – In EXPEDT: k l s c l                ! last l is for list




          Slide 63             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
    GSAS: spiraling in on the minimum and final structure

• May have to refine in quite a spiral manner
• Initially - have found circular refinement to be more controllable than
  combined refinement to be more controllable
   – heavy atoms using X-ray data
   – Oxygens using neutron data
• Restraints - problem with cemented structure vs having the structure fall
  apart
    – If restraints cement the structure, turning off restraints; doing small numbers of
      cycles and manually resetting errant atoms can get things rolling quite nicely.
    – Relaxing restraints sometimes can improve the regular co-ordination. !?
• If structure goes haywire, it can be easier to start again from the initial
  model
         • Wall paper bubble effect - tighten one errant atom causes 1 to 4 more to go
           out
• Be keen to exchange experiences on this

       Slide 64             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
GSAS: lessening the tedium: batch file control of the refinement :
                                                           ( fully ordered model)
 – Combatting impatience - tedious refinement strategy
 – Can leave a strategy to run overnight
    • (though you may suffer for this)
    • can be better to look after set periods of time and reset
      wandering atoms - which can go walk-about even if
      constrained on a problematic refinement involving
      lots of pseudo-symmetry.
 – Following examples for DOS / Windows (Linux / Unix is
   more flexible)
 – The @m command can be used to log a command
   sequence to a file to server as the starting point for
   editing a custom macro file.

   Slide 65             AGU 2002: “hints and tricks for using GSAS Rietveld”
              Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: lessen the tedium: batch file control of the refinement :
             (EXPEDT Example: script to increase the refined angular range)

                                         p                 !   powder setup
                                         h                 !   histogram setup
• In this case setting up                e 1               !   edit histogram 1 (X-ray)
  histogram 1 (powder XRD)               t                 !   set end of two theta
                                         70                !   set 70 degrees
                                         /                 !   confirm this then exit
• File titled 70_2t_x.txt                x
                                         x
• The BAT control file would             x
                                         x
  then enabled (“use”) all
  relevant histograms and run
  powpref after this file before
  going through a genles run.




          Slide 66             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
        GSAS: lessen the tedium: batch file control of the refinement :
         (EXPEDT Example: changing the bond restraint weighting)

                                       k    !     don't make a backup of the file
                                       l    !     least squares
• File titled bondr10.txt              s    !     soft constraints
                                       d    !     bond length restraints
                                       f 10 !     set bond restr. weighting to 10
                                       x    !     exit expedt
                                       x
                                       x
                                       x




        Slide 67             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
         GSAS: lessen the tedium: batch file control of the refinement :
                   (EXPEDT Example: only refining on neutron data)

                                       k
                                       l          !   least squares
• File titled neuonly.txt              s          !   soft restraints menu
                                       u 1        !   use histogram 1 - X-rays
                                       n          !   set to no
                                       u 3        !   use histogram 3 - neutron
                                       y          !   set to yes
                                       x
                                       x
                                       x




        Slide 68             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: lessen the tedium: batch file control of the refinement :
            (EXPEDT Example: refine heavy metal framework atoms)

                           k                 !   don't make a backup of the file
                           l                 !   least squares
• File titled              a                 !   atom options
                           v   1:324 -x      !   get rid of any X parameters refining
   ref_fmh.txt             q                 !   quit atom list
                           v   1:324 -u      !   get rid of any UISO parameters refining
                           q                 !   quit atom list
                           v   1:324 -f      !   get rid of any FRAC parameters refining
                           q                 !   quit atom list
                           v   29:108 x      !   set framework M sites refine on coords
                           q                 !   quit atom list
                           x
                           x
                           x




          Slide 69             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: lessen the tedium: batch file control of the refinement :
             (EXPEDT Example: refine light metal framework atoms)

                           k                 !   don't make a backup of the file
                           l                 !   least squares
• File titled              a                 !   atom options
                           v   1:324 -x      !   get rid of any X parameters refining
   ref_fml.txt             q                 !   quit atom list
                           v   1:324 -u      !   get rid of any UISO parameters refining
                           q                 !   quit atom list
                           v   1:324 -f      !   get rid of any FRAC parameters refining
                           q                 !   quit atom list
                           v   1:28 x        !   set framework M sites refine on coords
                           q                 !   quit atom list
                           x
                           x
                           x




          Slide 70             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: lessen the tedium: batch file control of the refinement :
          (EXPEDT Example: refine interstitial metal atoms - less vacancies)

                           k                 !   don't make a backup of the file
                           l                 !   least squares
• File titled              a                 !   atom options
                           v   1:324 -x      !   get rid of any X parameters refining
   ref_int.txt             q                 !   quit atom list
                           v   1:324 -u      !   get rid of any UISO parameters refining
                           q                 !   quit atom list
                           v   1:324 -f      !   get rid of any FRAC parameters refining
                           q                 !   quit atom list
                           v   133:144 x     !   set interstitial Met to refine
                           v   147:154 x     !   set interstitial Met to refine
                           v   157:162 x     !   set interstitial Met to refine
                           x
                           x
                           x




          Slide 71             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: lessen the tedium: batch file control of the refinement :
                                                     (EXPEDT Example: refine oxygens)

                           k                 !   don't make a backup of the file
                           l                 !   least squares
• File titled              a                 !   atom options
                           v   1:324 -x      !   get rid of any X parameters refining
   refoxy.txt              q                 !   quit atom list
                           v   1:324 -u      !   get rid of any UISO parameters refining
                           q                 !   quit atom list
                           v   1:324 -f      !   get rid of any FRAC parameters refining
                           q                 !   quit atom list
                           v   163:324 x     !   set oxygens to refine
                           q                 !   quit atom list
                           x
                           x
                           x




          Slide 72             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
          GSAS: lessen the tedium: batch file control of the refinement :
                                                         (EXPEDT Example: refine UISO)

                           k                 !   don't make a backup of the file
                           l                 !   least squares
• File titled              a                 !   atom options
                           v   1:324 -x      !   get rid of any X parameters refining
   refoxy.txt              q                 !   quit atom list
                           v   1:324 -u      !   get rid of any UISO parameters refining
                           q                 !   quit atom list
                           v   1:324 -f      !   get rid of any FRAC parameters refining
                           q                 !   quit atom list
                           v   1:324 u       !   set UISO of all atoms to refine
                           q                 !   quit atom list
                           x
                           x
                           x




          Slide 73             AGU 2002: “hints and tricks for using GSAS Rietveld”
                     Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
            GSAS: lessen the tedium: batch file control of the refinement :
                 (Create a Batch File to follow your desired command sequence)
                                             expedt model < batchjob\bondr1.txt
• File titled: refine.bat                    echo step 1 bond weight > autolog.txt
                                             expedt model < batchjob\xrayonly.txt
• In early stage of                          echo step 2 XRAYS ONLY >> autolog.txt
  refinement, a “cycle” of                   expedt model < batchjob\ref_fhm.txt
  refinement involves:                       genles model
                                             echo step 3 completed >> autolog.txt
    –   Set bond restraint weight
                                             expedt model < batchjob\ref_flm.txt
    –   Enable only X-ray data               genles model
    –   refine framework metal atoms         echo step 4 completed >> autolog.txt
    –   refine interstitial atoms            expedt model < batchjob\neuonly.txt
    –   Enable only Neutron data             echo step 5 NEUTRON ONLY >> autolog.txt
                                             expedt model < batchjob\refoxy.txt
    –   refine light oxygen atoms
                                             genles model
    –   refine constrained UISO              echo step 6   completed >> autolog.txt
• Batch files can be made more               expedt model < batchjob\refuiso.txt
  complicated with respect to                genles model
  logging what is happening                  echo step 7   completed >> autolog.txt



            Slide 74             AGU 2002: “hints and tricks for using GSAS Rietveld”
                       Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                 GSAS : If the refinement is not happy
• The tools are there for difficult refinements, but:
   – May not be easy!
   – May only find problems when in the middle of the refinement
      • Impurities in many and varied forms
      • XRD and Neutron data are different enough
          – different impurities showing up
          – different systematic effects
          – different volumes of sample having their effect
      • Wrong spacegroup
      • Non-optimum atom ordering
      • Non-optimum tilt model
      • Extra elements in the sample - have you used a microprobe?

      Slide 75              AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
  GSAS : “wall paper bubble effect trying to
    keep all bonds physically reasonable
• One problem trying to keep everything physically
  reasonable: trying to fix gives a “wall paper bubble
  effect” - fixed one bond causes 1 to 5 other bonds to
  become physically unreasonable.
• Suggestions on this appreciated (though this could be
  implying data purity problems)
   – Has been stated that the above can be a common
     problem due to pseudo-symmetry and wrong
     spacegroup
   – Though in this example looks like wrong chemistry
     and some octahedra really being tetrahedra
       Slide 76             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
GSAS : Combined refinement on both XRD and Neutron in C1
     (bond length problems - “bubbles” - to stomp on)
             (which imply problems with the model or symmetry).


 X-ray 7.6% R(F**2)                                   Neutron 4.2% R(F**2)
  (~3.8% R Bragg)                                          (~2.1% R Bragg)




      Slide 77             AGU 2002: “hints and tricks for using GSAS Rietveld”
                 Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
  Despite a good fit : model can still have problems : wrong
chemistry was defined and structure not physically reasonable.

• In this case, GSAS refined model was used to try and
  determine twin laws on the single crystal data using
  “Jana” for refinement and Simon Parsons and Bob
  Gould’s “Rotax” (Fo/Fc) twinning software; and pre-
  defined twinning models.
• Refinement in R3 then C1 with and without various twin
  models gave a final R factor of 4.6%, untwinned in R3.
• Using the powder refined model as a starting point, it
  would seem that “Jana” was able to minimize on the
  single crystal data in R3 (and C1) where other programs
  possibly failed.

       Slide 78             AGU 2002: “hints and tricks for using GSAS Rietveld”
                  Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
WinGX and Platon for validation of the structure and looking for
                      higher symmetry

 • EXPGUI can output Shelx INS and Platon SPF files.
 • Exporting a Shelx file can then be read by WinGX and
   transferred to all its relevant callable programs
    – Structure plotting
    – Geometry checking
    – Platon




        Slide 79             AGU 2002: “hints and tricks for using GSAS Rietveld”
                   Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
           WinGX for Windows single crystal suite
           Validation and Structure Checking
•   Platon (Addsym, etc)
•   CIF Validation
•   Parst
•   GEOM
•   THMA 14c
•   IDEAL
•   SYMMOL
•   WTANAL
•   R-tensor



           Slide 80             AGU 2002: “hints and tricks for using GSAS Rietveld”
                      Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                      Void checking using Platon
In the case the pink balls are showing where significant voids are in located in
the structure.




           Slide 81              AGU 2002: “hints and tricks for using GSAS Rietveld”
                       Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
 Graphically interacting with programs that are
            GSAS EXP file friendly

         GUI WinORTEP                                                GUI WinSTRUPLO
(http://www.chem.gla.ac.uk/~louis/software/ortep3/)            (http://www.chem.gla.ac.uk/~louis/software/struplo/)




                Slide 82               AGU 2002: “hints and tricks for using GSAS Rietveld”
                             Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
         Photorealistic rendering of structures
        GUI WinORTEP / GUI Struplo / WinGX
http://www.ccp14.ac.uk/tutorial/wingx/
• Can open a wide variety of file
   formats including GSAS!




           Slide 83             AGU 2002: “hints and tricks for using GSAS Rietveld”
                      Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
  Ton Spek’s Platon Addsym - finding extra symmetry and
      exploring symmetry in simple to complex polymeric
                                              inorganics

• WWW: http://www.cryst.chem.uu.nl/platon/
• One of the best programs for finding missing
  symmetry from crystal structure information.
• Now has enhanced subcell finding
• Now has enhanced defaults for inorganics




    Slide 84             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
   Ton Spek’s Platon Addsym - another spectacular example

• Triclinic Cell - P1
   – structure calculated
     by an-initio
     methods
   – (96 independent
     Carbon atoms)




         Slide 85             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
              Ton Spek’s Platon Addsym - spectacular example
                         Run Platon’s Addsym in default mode

• Addsym finds the
  true cell - which is a
  1/8th subcell
   – (3 independent
     Carbon atoms)
   – Monoclinic P 21/c
   – (compared to 96
     atoms in the starting
     structure)
   – Can be just as
     effective for ab-
     initio calculations on
     minerals.
         Slide 86             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
    Platon’s Addsym - finding extra symmetry in
                  hand- build inorganic models
• In the GSAS refined ceramic - original
  starting “model” was hand-built using crystal
  chemical arguments in R3

• Platon’s Addsym (default values) gives R-3c
  – plus option of a new Shelx RES file with the
    structure in the new spacegroup
  – and the directions to find the extra symmetry
    elements from the old R3 model

    Slide 87             AGU 2002: “hints and tricks for using GSAS Rietveld”
               Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
   Platon’s Addsym - finding extra symmetry in
            powder refined structure in triclinic

• Model refined in C 1
• Platon’s Addsym can get back to R3 except
  one interstitial metal site seems to be
  breaking the symmetry and keeping the
  triclinic symmetry.
• Got to be careful how you use this :
  – e.g., increasing the values for the defaults can get
    you back your “ideal” non-tilt model


   Slide 88             AGU 2002: “hints and tricks for using GSAS Rietveld”
              Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk
                                       Summary
• Help show some of the potential of using GSAS and EXPGUI for
  some of your mineralogical and inorganic powder samples.
• Show other programs that can be of assistance - Platon, WinGX,
  Jana, VCTCONV, Powder v 4, etc
• Many of the listed resources are available or mirrored at:

                    http://www.ccp14.ac.uk
Thanks:
    –   Bob von Dreele and Alan Larsen - GSAS Rietveld
    –   Brian Tony - EXPGUI
    –   Ton Spek - Platon
    –   Mark Bowden - Vctconv
    –   Louis Farrugia - WinGX
    –   Ian Grey, Gus Mumme, Bob Roth, et al - High-tech ceramic example


         Slide 89             AGU 2002: “hints and tricks for using GSAS Rietveld”
                    Lachlan M. D. Cranswick (l.m.d.cranswick@dl.ac.uk) http://www.ccp14.ac.uk

				
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