APPENDIX A - Symmetry File DescriptionThe input symmetry data file used in calculating the Patterson Peaks was based on the Enraf-Nonius MolEN SPACE.ASC file. Information was added -- all origin choices, description of the origin, special positions, and data needed for table headings -- and corrections were made; the original file now constitutes only about 20% of the total file. A detailed description of the input symmetry data file follows: Columns Format Name Description Record 1 1- 4 I4 PAGE Starting page number for output tables (useful when preparing tables a few at a time). Record 2 1- 4 I4 NSPG Space group number (e.g., "14" for P21/c) 5- 8 I4 SYSTEM Crystal system 1 = triclinic 2 = monoclinic 3 = orthorhombic 4 = tetragonal 5 = trigonal (if R, rhombohedral axes) 6 = hexagonal (if R, hexagonal axes) 8 = cubic 9- 12 I4 NCENT Centrosymmetry indication 0 = no inversion center AT ORIGIN OF CELL 1 = inversion center AT ORIGIN OF CELL 13- 15 3X (blank) 16- 23 A8 SGNAM Space group name (short form) 24 A1 KAXIS Axis choice (e.g., "b" for b axis unique) 25- 26 I2 KCHOICE Setting or origin choice (if applicable) 27- 31 5X (blank) 32- 47 A16 SGNAMFUL Space group name (long form) 48 A1 SCH1 The three parts of the Schoenflies symbol 49- 50 A2 SCH2 for the space group (main, superscript, 51- 52 A2 SCH3 and subscript) LEFT JUSTIFIED 53- 56 I4 NEQV Number of general equivalent position records to follow for the general position (do NOT include records for positions generated by lattice centering or by an inversion center AT ORIGIN OF CELL) 57- 60 I4 NORG Number of origin description records (1-2) Record 3 1- 2 I2 IA(1) Lattice centering code 0 = Primitive 1 = A-centered 2 = B-centered 3 = C-centered 4 = F-centered 5 = I-centered 6 = R-obverse 7 = Hexagonal 3- 26 12I2 IA(i) Extinction conditions (IA(2)-IA(13)) Records 4 (total of NORG records) 1- 80 A80 ORIG Description of unit cell origin in text form, using one to two records. The back-slash character (\) indicates where a new line begins. Record 5 1- 4 I4 SMULT Site multiplicity 5 1X (blank) 6 A1 WYCKLET Wyckoff letter identifying position 7 1X (blank) 8- 23 A16 SSYM Site symmetry Records 6 (total of NEQV records) 1- 45 15I3 IA Matrix/vector form of equivalent positions (do NOT include records for positions generated by lattice centering or by an inversion center AT ORIGIN OF CELL) Record 7 (only if WYCKLET above is not "a") 1- 4 I4 SMULT Site multiplicity 5 1X (blank) 6 A1 WYCKLET Wyckoff letter identifying position 7 1X (blank) 8- 23 A16 SSYM Site symmetry Records 8 (total of SMULT records -- see Record 7) 1- 45 15I3 IA Matrix/vector form of equivalent positions (note: for the special positions, include all positions except those generated by lattice centering) Repeat Record 7 and Records 8 as needed to include ALL sets of special positions for this space group. Then, begin again with a Record 2 to start the next space group. Example: The entry in the input symmetry data file for space group #14, unique axis b, second cell choice (P21/n): 67 14 2 1 P21/n b 2 P 1 21/n 1 C5 2h 2 1 0 0 3 0 0 0 0 0 0 0 0 1 0 at -1 4 e 1 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 1 2 -1 0 0 1 2 0 1 0 1 2 0 0 -1 2 d -1 1 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 0 0 0 1 2 0 0 0 2 c -1 1 2 0 0 0 0 0 0 0 0 1 2 0 0 0 0 0 0 0 0 1 2 0 0 0 0 0 0 0 0 2 b -1 0 0 0 0 0 0 0 0 0 0 1 2 0 0 0 1 2 0 0 0 1 2 0 0 0 0 0 0 0 0 2 a -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 0 0 0 1 2 0 0 0 1 2 0 0 0 |
Last updated: April 7, 2005 Comments: URL: http://www.chemistry.msu.edu/staff/ward/PattPeaks/brief_app-a.shtml |