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Methods, Problems and Solutions

Single Crystal Twinning Software and Web Resources

The CCP14 Homepage is at http://www.ccp14.ac.uk

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Crystals for Windows (single crystal suite)
  • David Watkin, Richard Cooper, et al. (david.watkin@chem.ox.ac.uk or richard.cooper@chemical-crystallography.oxford.ac.uk)
  • Incorporating Simon Parson and Bob Gould's ROTAX. Determining the Twin Matrix from Fo/Fc data
  • Option is presently accessed via the Crystals menu system under: Development, ROTAX
  • Download Crystals via the CCP14 Crystals page
  • Original Rotax webpages.


Dirax for VMS, MSDOS, SGI or Linux

Platon for UNIX (and Windows port by Louis Farrugia)
  • Ton Spek (a.l.spek@chem.uu.nl)
  • TwinRotMac function within Platon. TwinRotMac: "Determine Twin Matrix from Fo/Fc Data"
  • Download Platon for UNIX/Windows via the CCP14 Platon page

  • Extract from the TwinRotMac help page at: http://www.cryst.chem.uu.nl/platon/pl000606.html | [ CCP14 UK Web Mirror]

  • "This function carries out an after-the-fact analysis for missed or unaccounted for twinning from the analysis of an Fo/Fc CIF.
    Ideally, twinning is already discovered in the early stages of data collection and taken care of. This applies in particular for data collected on CCD detector systems. Exceptions are cases of (pseudo)merohedral twinning.
    This routine addresses cases of (reticular)(pseudo) merohedral twinning. Cases where data are based on a the artificially higher volume twin lattice are not covered. (i.e. monoclinic structure in orthorhombic supercell twin lattice).
    A tentative rotation twin axis and associated matrix is produced.
    The analysis is based on the well known fact that unaccounted for twinning shows up in a significant number of reflections with I(obs) much greater than I(calc).
    The program needs an '.fcf' file (e.g. shelxl.fcf) for the analysis. "

ROTAX for Windows - Simon Parsons and Bob Gould

Twindex (Twinning Analysis Program) (GPL Licence - Redhat Linux binaries with C source code)
  • Paul Boyle (boyle@laue.chem.ncsu.edu)
  • twindex is a program used for analysis of diffraction patterns of non merohedral twins

    There are three modes of operation:

    Select Mode: program takes a SHELX HKLF file and selects a specified number of reflections at random and creates a file for input into Duisenberg's DIRAX program. Each reflection is only selected once per list created. There are several criteria to evaluate the suitability of reflections.

    Reindex Mode: This mode is used when the data was collected on a composite cell. The user is prompted for the orientation matrix with which the data was collected, the number of twin components, and a twin law (or the orientation matrices for the single domain fragments). The program reads a SHELX HKLF 4 file and outputs a SHELX HKLF 5 file.

    Overlap Mode: This mode is used when the data was collected on a single fragment of the twin and the orientation matrix(cies) (or twin law) is (are) known for the other twin fragment(s). The program takes a SHELX HKLF 4 file and produces a SHELX HKLF 5 file.

  • Original at ftp://ftp.xray.ncsu.edu/pub/X-ray/twindex/
  • CCP14 UK Web Mirror

The Merohedral Crystal Twinning Server

Daniel B. Litvin "twinlaws" Software
  • Daniel B. Litvin (u3c@psu.edu)
  • Original at http://www.bk.psu.edu/faculty/litvin/Download.html
  • [UK CCP14 Web Mirror] | [Canadian CCP14 Web Mirror] | [US CCP14 Web Mirror]

    For a phase transition between a high symmetry phase of non-magnetic point group symmetry G and low symmetry phase of non-magnetic point group F, this program calculates:

    1. The coset and double coset decomposition of the point group G with respect to the point group subgroup F.
    2. Indexes the domain states S(i) which arise in such a transition.
    3. Calculates the point group symmetry F(i) of each domain state.
    4. Calculates the permutations of the domain states S(i) under the action of elements g of the point group G.
    5. Calculates all domain pair {S(i),S(j)} in each class of domain pairs.
    6. Calculates a representative domain pair {S(1),S(j)} from each class of domain pairs.
    7. Calculates for each representative domain pair its symmetry group J(1,j) and its twinning group K(1,j).
    8. Calculates the domain pair {S(1), gS(1)} and its symmetry and twinning groups.
    9. Calculates the symmetry and twinning groups of an arbitrary domain pair {S(i),S(j)}.
    See publication "Non-Magnetic Twin Laws" by J. Schlessman and D.B. Litvin, Acta Cryst. (1995) A51, 947-949.

TWIN 3.0 / TWIN3.0 for Windows
  • The principle features of the program are :
    1. Single crystal data sets can be tested if they are subject to twinning by merohedry.
    2. The volume fractions of the different twin domains can be estimated.
  • Volker Kahlenberg and T. Messner, FB Geowissenschaften, Kristallographie, Universitšt Bremen, Bremen, Germany.
  • The program is freely available upon request to (Volker.Kahlenberg@uibk.ac.at)
  • Volker Kahlenberg's homepage: http://www.uibk.ac.at/c/c7/c714/staff/kahlenberg0.html
  • Reference: Kahlenberg, V. & Messner, T. (2001). TWIN3.0 - a program for testing twinning by merohedry. J. Appl. Cryst. 34, 405

TMACLE (Source Code)
  • By Armel Le Bail (lebail@univ-lemans.fr)
  • Tmacle: crystal structure refinement program designed for crystals with twinning by twin lattice symmetry (TLS) (no evidence for doubling of spots). It was built from a multi-pattern Rietveld code, changing the multi-pattern option to a multi twin domain option.
  • Recommended reading from the Tmacle manual:
    1. G. DONNAY and J.D.H. DONNAY, CANADIAN MINERALOGIST, 12, 422-425 (1974)
    2. T. ARAKI, Z. KRISTALLOGR. 194, 161-191 (1991)
  • References on its successful use:
    1. A. LE BAIL, Y. GAO and C. JACOBONI, EUR. J. SOLID STATE INORG. CHEM. 26, 281-288 (1989)
    2. A. HEMON, A. LE BAIL and G. COURBION, J. SOLID STATE CHEM. 81, 299-304 (1989)
    3. A. LE BAIL, Y. GAO, J.L. FOURQUET and C. JACOBONI, MAT. RES. BULL. 25, 831-839 (1990)
    4. M.C. MORON, A. LE BAIL and J. PONS, J. SOLID STATE CHEM. 88, 498-504 (1990)
    5. J.J. ROUSSEAU, B. BOULARD, H. DUROY and J.L. FOURQUET, EUR. J. SOLID STATE INORG. CHEM. 27, 913-924 (1990)
    6. Y. GAO, J. GUERY, A. LE BAIL and C. JACOBONI, J. SOLID STATE CHEM. 98, 11-24 (1992)
    7. M. LEBLANC, G. FEREY and R. DE PAPE, ACTA CRYST. C41, 657-660 (1985)
    8. A. LE BAIL, C. JACOBONI, M. LEBLANC, R. DE PAPE, H. DUROY and J.L. FOURQUET, J. SOLID STATE CHEM. 77, 96-101 (1988)
    9. J. OSTORERO and M. LEBLANC, ACTA CRYST. C46, 1376-1378 (1990)

  • From the Tmacle manual:
             GOOD LUCK 
             IT'S VERY HARD ! DON'T YOU THINK SO ?
             ONLY THE BOSS SAID THAT IT IS EASY, BUT HE NEVER TRIED !
    
             TO HAVE THE SOLUTION DEPENDS ON YOU, NOT ON THIS PROGRAM
             WHICH IS JUST ABLE TO TEST YOUR HYPOTHESIS..............
  • Original at [ http://sdpd.univ-lemans.fr/museum/] | [ http://sdpd.univ-lemans.fr/museum/tmacle92.zip]
  • Mirrors: [ CCP14 UK Mirror] | [ CCP14 UK Mirror]

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