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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.

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Presentation on theme: "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."— Presentation transcript:

1 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. WWW:

2 AGU 2002: “hints and tricks for using GSAS Rietveld”
Hand Written Notes Free Zone they are on the web Slide 2 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

3 AGU 2002: “hints and tricks for using GSAS Rietveld”
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

4 AGU 2002: “hints and tricks for using GSAS Rietveld”
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

5 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

6 AGU 2002: “hints and tricks for using GSAS Rietveld”
by Bob von Dreele and Alan Larson - ftp://ftp.lanl.gov/public/gsas/ CCP14 based resources: 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

7 AGU 2002: “hints and tricks for using GSAS Rietveld”
GSAS: Some Relevant Background by Bob von Dreele and Alan Larson Menu based control Available for Windows / DOS / Linux / SGI Separate GUI by Brian Toby (EXPGUI) Combined X-ray / Neutron / Single Crystal / Powder Diffraction Integrated Fourier map generation and viewing Restraints Bond angle Bond length Planar Total Chemistry / charge balance Chiral volume Phi/psi group Torsion angle Manual Marquadt damping Atom shift limits Lots of other features Slide 7 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

8 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.) Slide 8 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

9 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

10 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

11 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 (or import structure from Powder Cell *.cel, CIF, GSAS, MSI *.xtl, Platon *.spf) Slide 11 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

12 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

13 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

14 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

15 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

16 Bob von Dreele’s comments on Damping
“Damping - I never use damping in any of my refinements unless I actually need it. There is an option in the LS print menu for listing the "summary table of shift/esd" that is helpful for identifying ocsillating parameters. One should first try no damping and then use it only where necessary. Invoking it early can cause trouble. Another option for atom positions is to "limit the shift" to 0.5A or whatever to keep an early refinement from going off base.” Slide 16 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

17 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 17 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

18 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 18 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

19 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 19 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

20 Note from Bob von Dreele on POLA
Typically iparm files will have "incorrect" POLA values. You might suggest "good" values for graphite monochromators. Thus while calculated values can be determined, experimentally determined values may be recommended. Not only for laboratory systems, but also synchrotron data where ideal values might be assumed. In this case using cubic annealed Y2O3 (10.6Å - IA3) Slide 20 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

21 POLA for your Diffractometer and graphite monochromator
POLA correlates with thermals so be careful checking how robust the resulting value is. (following is determined using annealed Y2O3) Slide 21 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

22 Another way: POLA, IPOLA and diffracted beam graphite monochromator
Set IPOLA to 1 (POLA should now be cos2 2 of the monochromator.) In the case of Graphite 002 reflection: 2 = (d=3.3480Å). cos2 2=0.80 Mainly due to problems such as mosaic spread - POLA refines on this diffractometer (again using annealed Y2O3) to 0.911 Slide 22 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

23 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 23 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

24 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 24 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

25 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 (is preferable to use this instead of “zero offset”) Slide 25 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

26 “Choice of "shft" vs "ZERO" is most important.
Note from Bob von Dreele on shft “Choice of "shft" vs "ZERO" is most important. Diffractometers are aligned to make ZERO=0.000 and the sample is "never" in the right place to make shft=0.0. So always refine shft for Bragg-Brentano data. Synchrotron data is different as the zero can be off and other systematic effects will look like "shft" or "trns". If sample is transparent on B-B diffractometers (especially pharmaceuticals!) then trns should be refined.” Slide 26 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

27 Brian Toby’s EXPGUI: Profile Screen in EXPGUI with shft
Slide 27 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

28 It helps if you refine the appropriate parameters.
Estimated Standard Deviations (ESD) vs Standard Deviations An ESD is the estimated uncertainty derived from a “single measurement”. A Standard Deviation is an uncertainty obtained from collecting “multiple measurements”. Rietveld programs ESDs are fine as ESDs go, but they can under estimate “probable error”. If you want to know what the “Standard Deviation” is, multiple sample preparation, packing and collection of the data a statistically valid number of times is a way to proceed. It helps if you refine the appropriate parameters. Slide 28 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

29 AGU 2002: “hints and tricks for using GSAS Rietveld”
Unit-cell “a-axis” parameter of monoclinic zirconia collected repetitively and refining zero offset Each sample was packed separately and run for a structure refinement quality dataset; Cu Tube, 15 to 154 at step size on a Philips 3050/X’pert Bragg Bretano powder diffractometer. Slide 29 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

30 AGU 2002: “hints and tricks for using GSAS Rietveld”
Rietveld ESD on Unit cell parameter vs the standard deviation from multiple packings and measurements Rietveld ESD on the “a” unit-cell parameter: Standard Deviation on the “a” unit-cell parameter: Standard deviation from multiple measurements is over 3 times the estimated standard deviation (ESD) from a single measurement The IUCr (International Union of Crystallography) has defined various units including “standard uncertainties” but common nomenclature is being used here. Slide 30 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

31 AGU 2002: “hints and tricks for using GSAS Rietveld”
Unit-cell “a-axis” parameter of monoclinic zirconia collected repetitively and refining sample displacement Each sample was packed separately and run for a structure refinement quality dataset; Cu Tube, 15 to 154 at step size on a Philips 3050/X’pert Bragg Bretano powder diffractometer. Slide 31 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

32 AGU 2002: “hints and tricks for using GSAS Rietveld”
Rietveld ESD on Unit cell parameter vs the standard deviation from multiple packings and measurements Rietveld ESD on the “a” unit-cell parameter: Standard Deviation on the “a” unit-cell parameter: Standard deviation from multiple measurements is not significantly different from the estimated standard deviation (ESD) of a single measurement However, you can still get problems with accuracy due to misalignment in different powder diffractometers. Two theta offset should be a constant of the diffractometer Sample displacement should vary with each inserted sample Never refine both two-theta and sample displacement Slide 32 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

33 Brian Toby’s EXPGUI: Writing your own importing options
EXPGUI: customization notes on the web at Copy over an existing import script and edit it to work with your new data format in tcl/tk. Slide 33 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

34 New(ish) Features in Brian Toby’s EXPGUI
Graphically define the background Graphically exclude regions Can export structures to Cif/Shelx/Platon format (Addsym, etc) / MSI *.xtl formats Slide 34 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

35 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 35 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

36 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 36 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

37 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 37 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

38 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 38 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

39 Brian Toby’s EXPGUI: Graphically Excluding Regions (2 of 3)
Point and click to select excluded regions Slide 39 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

40 Brian Toby’s EXPGUI: Graphically Excluding Regions (3 of 3)
Run powpref and genles for this to take effect Slide 40 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

41 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 41 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

42 AGU 2002: “hints and tricks for using GSAS Rietveld”
Brian Toby’s EXPGUI: Le Bail fitting to get the whole profile fit the data before structure refinement Various tricks may be required. Fix the “Scale Factor”. It is meaningless to refine the scale factor when doing a Le Bail fit. Brian Toby trick: Run zero cycles until the intensities roughly match before releasing any other parameters (peak profile, unit cell, zero offset) Fit the background manually with Chebyshev coefficients within bkgedt instead of refining the background. This can save you a lot of pain Running Powpref resets the Le Bail intensities and you have to turn off all parameters and rematch the intensities with the pattern : so you would normally avoid doing this unless you make a change to the “spacegroup” or other relevant parameters such as the “peak cutoff” Slide 42 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

43 Important to know the instrumental and synchrotron beamline constants
Brian Toby’s EXPGUI: Why Isn’t this Synchrotron data fitting? - 1 Important to know the instrumental and synchrotron beamline constants Slide 43 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

44 Polarization is incorrect - is zero instead of ~1 (0.9 to 1)
Brian Toby’s EXPGUI: Why Isn’t this Synchrotron data fitting? - 2 Polarization is incorrect - is zero instead of ~1 (0.9 to 1) Reset all synchrotron data sets / histograms to the correct value The beamline should determine this parameter for users Slide 44 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

45 Brian Toby’s EXPGUI: Why Isn’t this Synchrotron data fitting? - 3
With roughly correct polarization value (set at 1), things are looking better (need to get the accurate value) Slide 45 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

46 GSAS and example ceramic / polymeric inorganic problem
In this example, a perovskite based ceramic relevant to the wireless communications and the mobile phone industry (High Q ferroelectric) >120 atoms in R3 >320 atoms in C1 54 possible “split occupancy” framework metal sites 54 possible atom / vacancy interstitial sites 162 oxygen sites >1600 bond restraints >200 atom constraints >150 atoms linked within a single constraint Slide 46 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

47 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 47 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

48 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 48 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

49 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 49 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

50 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 50 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

51 AGU 2002: “hints and tricks for using GSAS Rietveld”
GSAS : YES! - at present the only effective Rietveld system for these types of large problems GSAS (by the Anna Karenina principle - a happy family): Can handle large numbers of atoms and restraints Large variety of restraints Menu based control amenable to scripts and automation Easy enabling and disable of histograms Integrated Fourier map including peak search TOF Neutron / EDX as well Other Rietveld Programs affected by one or more of the following problems Cannot handle large numbers of atoms or restraints Don’t have many types of restraints Manual editing of ASCII files or GUIs that do not easily allow quick changes to large numbers of atoms Problematic enabling and disabling of restrains and histograms No integrated Fourier map generation and viewing Can only handle constant wavelength neutron and angular dispersive X-ray diffraction data. Slide 51 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

52 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 52 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

53 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, Slide 53 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

54 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 54 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

55 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 55 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

56 GSAS: Individual Histogram Weighting (using Sum(w*d**2) as a guide)
Set via EXPEDT (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 56 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

57 GSAS: If you DON’T Use Histogram Weighting
X-ray 8.0% R(F**2) Neutron 28.1% R(F**2) Slide 57 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

58 GSAS: If you DO Use Histogram Weighting
X-ray 8.3% R(F**2) Neutron 11.7% R(F**2) Slide 58 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

59 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 59 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

60 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: Slide 60 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

61 AGU 2002: “hints and tricks for using GSAS Rietveld”
VCT for Refinement (1 of 4) Variable Count Time data (as collected - CAD4 style) Slide 61 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

62 AGU 2002: “hints and tricks for using GSAS Rietveld”
VCT for Refinement (2 of 4) Variable Count Time data (normalised as FCT) Slide 62 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

63 AGU 2002: “hints and tricks for using GSAS Rietveld”
VCT for Refinement (3 of 4) Variable Count Time data (normalised as FCT) Slide 63 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

64 AGU 2002: “hints and tricks for using GSAS Rietveld”
VCT for Refinement (4 of 4) Variable Count Time data (displayed as VCT) Slide 64 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

65 Getting Madsen and Hill VCT data into GSAS ESD format
Mark Bowden’s VCTCONV for DOS (runs on Windows) Download: Slide 65 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

66 Using Nita Dragoe’s Powder v4 for Windows
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: Open the x,y,z “free ascii” data Save as GSAS CW ESD format Done! Slide 66 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

67 AGU 2002: “hints and tricks for using GSAS Rietveld”
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. One solution is to use a spreadsheet program that allows for flexibility and extendability (MS-EXCEL for Windows) Slide 67 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

68 Restrained refinement in GSAS: setting up an EXCEL spreadsheet
CCP14 based tutorial and example files at : 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: Coue: Atom constraints Total cell contents and/or charge balance constraints If applicable, other scripts for controlling GSAS Slide 68 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

69 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 k l a Use Windows “cut and paste” (import macro file command) while in the relevant menu Slide 69 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

70 AGU 2002: “hints and tricks for using GSAS Rietveld”
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. 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 70 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

71 AGU 2002: “hints and tricks for using GSAS Rietveld”
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: k l s d More details given at: Slide 71 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

72 AGU 2002: “hints and tricks for using GSAS Rietveld”
GSAS: Getting > 1600 bond restraints in a GSAS happy format In Crystals running the script to generate the list of restraints #use struct.txt (which contains - search outward to 3.3Å to also get Oxy-Oxy bonds: and all symmetry equivalent bonds) #rele punch lengths.txt #DISTANCE OUTPUT PUNCH=RESTRAIN SELECT RANGE=LIMITS LIM end #rele punch dummy.txt Slide 72 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

73 AGU 2002: “hints and tricks for using GSAS Rietveld”
GSAS: Getting > 1600 bond restraints in a GSAS happy format Use a column able editor such as ConTEXT to change to desired bond lengths and ESDs E.g., Ca - O bond length = 2.3 ESD = 0.11 O-O bond length = 2.90 ESD = 0.31 (use histogram weighting on the bond restraints to tighten or loose their influence on the refinement) [CNTRL L] in ConTEXT to go in and out of column editing mode Slide 73 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

74 AGU 2002: “hints and tricks for using GSAS Rietveld”
GSAS: Getting > 1600 bond restraints in a GSAS happy format Use Scott Belmonte’s COUE software to convert the Crystals restraints into GSAS format Run Scott Belmonte’s GPL’d COUI program It is possible to do Ca* to O* mass defining of restraints in GSAS’s EXPEDT program but this method gives you complete control to easily make changes and then reinsert the restraints and know what is going on. Show due care as problems can occur with restraints not being inserted (or wrong atoms) due to search distance (k l s d f in expedt). Now in GSAS Macro format I Y I I I I I I etc, etc, etc, etc Slide 74 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

75 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 75 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

76 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 76 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

77 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 77 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

78 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”: Use - import macro file command while in the relevant menu Done! Slide 78 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

79 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 79 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

80 GSAS: turning off /on histograms, restraints, atoms in EXPEDT
Also can be done in GSAS’s EXPEDT k l s u The use command e.g., turn off X-ray data (histogram 1), turn on bond restraints (histogram 2) and neutron data (histogram 3) k l s ! Go into EXPEDT restraints menu u 1 ! Use histogram 1 - X-ray Data n ! No u 2 ! Use histogram 2 - Bond Restraints y ! Yes u 3 ! Use histogram 3 - Neutron Data x x x ! Exit EXPEDIT menus and quit Slide 80 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

81 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 81 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

82 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 Slide 82 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

83 AGU 2002: “hints and tricks for using GSAS Rietveld”
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) 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 83 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

84 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 e ! edit histogram 1 (X-ray) t ! set end of two theta ! set 70 degrees / ! confirm this then exit x In this case setting up histogram 1 (powder XRD) File titled 70_2t_x.txt The BAT control file would then enabled (“use”) all relevant histograms and run powpref after this file before going through a genles run. Slide 84 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

85 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 s ! soft constraints d ! bond length restraints f 10 ! set bond restr. weighting to 10 x ! exit expedt x File titled bondr10.txt Slide 85 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

86 AGU 2002: “hints and tricks for using GSAS Rietveld”
GSAS: lessen the tedium: batch file control of the refinement : (EXPEDT Example: only refining on neutron data) k l ! least squares 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 File titled neuonly.txt Slide 86 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

87 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 a ! atom options v 1:324 -x ! get rid of any X parameters refining q ! quit atom list v 1:324 -u ! get rid of any UISO parameters refining v 1:324 -f ! get rid of any FRAC parameters refining v 29:108 x ! set framework M sites refine on coords x File titled ref_fmh.txt Slide 87 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

88 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 a ! atom options v 1:324 -x ! get rid of any X parameters refining q ! quit atom list v 1:324 -u ! get rid of any UISO parameters refining v 1:324 -f ! get rid of any FRAC parameters refining v 1:28 x ! set framework M sites refine on coords x File titled ref_fml.txt Slide 88 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

89 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 a ! atom options v 1:324 -x ! get rid of any X parameters refining q ! quit atom list v 1:324 -u ! get rid of any UISO parameters refining v 1:324 -f ! get rid of any FRAC parameters refining 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 File titled ref_int.txt Slide 89 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

90 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 a ! atom options v 1:324 -x ! get rid of any X parameters refining q ! quit atom list v 1:324 -u ! get rid of any UISO parameters refining v 1:324 -f ! get rid of any FRAC parameters refining v 163:324 x ! set oxygens to refine x File titled refoxy.txt Slide 90 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

91 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 a ! atom options v 1:324 -x ! get rid of any X parameters refining q ! quit atom list v 1:324 -u ! get rid of any UISO parameters refining v 1:324 -f ! get rid of any FRAC parameters refining v 1:324 u ! set UISO of all atoms to refine x File titled refoxy.txt Slide 91 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

92 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 echo step 1 bond weight > autolog.txt expedt model < batchjob\xrayonly.txt echo step 2 XRAYS ONLY >> autolog.txt expedt model < batchjob\ref_fhm.txt genles model echo step 3 completed >> autolog.txt expedt model < batchjob\ref_flm.txt echo step 4 completed >> autolog.txt expedt model < batchjob\neuonly.txt echo step 5 NEUTRON ONLY >> autolog.txt expedt model < batchjob\refoxy.txt echo step 6 completed >> autolog.txt expedt model < batchjob\refuiso.txt echo step 7 completed >> autolog.txt File titled: refine.bat In early stage of refinement, a “cycle” of refinement involves: Set bond restraint weight Enable only X-ray data refine framework metal atoms refine interstitial atoms Enable only Neutron data refine light oxygen atoms refine constrained UISO Batch files can be made more complicated with respect to logging what is happening Slide 92 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

93 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 93 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

94 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 94 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

95 AGU 2002: “hints and tricks for using GSAS Rietveld”
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) (~3.8% R Bragg) Neutron 4.2% R(F**2) (~2.1% R Bragg) Slide 95 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

96 JANA Single Crystal and Powder Diffraction Refinement
Developed for handling inorganics / metals - commensurate and incommensurate by Vaclav Petricek and Michal Dusek Single crystal and powder diffraction (not Neutron Time of Flight (TOF)) Powder tutorial at: UNIX, Windows and Mac Os X Menu driven Complicated inorganic solid state structure refinement Commensurate, incommensurate and composite structures Electron density and anharmonic refinement (automatically sets the required symmetry constraints for anharmonic) Refinement of f’ and f’’ Equation editor based constraints make it possible to link any one parameter to another Can handle multiple twins Many other features Slide 96 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

97 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 97 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

98 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 98 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

99 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 99 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

100 Void checking using Platon
In the case the pink balls are showing where significant voids are in located in the structure. Slide 100 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

101 Graphically interacting with programs that are GSAS EXP file friendly
GUI WinORTEP (http://www.chem.gla.ac.uk/~louis/software/ortep3/) GUI WinSTRUPLO (http://www.chem.gla.ac.uk/~louis/software/struplo/) Slide 101 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

102 AGU 2002: “hints and tricks for using GSAS Rietveld”
Ton Spek’s Platon Addsym - finding extra symmetry and exploring symmetry in simple to complex polymeric inorganics WWW: 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 102 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

103 AGU 2002: “hints and tricks for using GSAS Rietveld”
Ton Spek’s Platon Addsym - another spectacular example Triclinic Cell - P1 structure calculated by an-initio methods (96 independent Carbon atoms) Slide 103 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

104 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 104 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

105 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 105 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

106 AGU 2002: “hints and tricks for using GSAS Rietveld”
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 106 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick

107 AGU 2002: “hints and tricks for using GSAS Rietveld”
Summary Help show some of the potential of using GSAS and EXPGUI. Do the Experiment with GSAS! (sample packings, different refinements) 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: Thanks: Bob von Dreele and Alan Larson - 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 107 AGU 2002: “hints and tricks for using GSAS Rietveld” Lachlan M. D. Cranswick


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