# NONSYM

SYMMETRY TOOLS PLATON HOMEPAGE

# Search for and analysis of non-crystallographic symmetry

A search for non-crystallographic symmetry in a structural model is done on two levels

1. # Intra-molecular

The point group symmetry of isolated molecules (residues) is determined following the SYMMOL algorithm of T. Pilati & A. Forni, J.Appl.Cryst. (1998), 31, 503-504.

Examples:

bucky.spf gives pointgroup Ih for C60.

c476.spf gives pointgroup Td for C476.

Note:

• Hydrogen atoms are left out of the analysis.

• The analysis is done for each discrete residue, starting with a distance tolerance of 0.1 and stepping up by 0.1 up to 0.8 until symmetry is detected.

• The starting point of the tolerance can be given optionally on the keyboard instruction.

Example: CALC NONSYM 0.5

Sample output of NONSYM/SYMMOL for cubane (space group R-3, site symm -3).
```
================================================================================
SYMMOL: Search for (additional) Molecular Symmetry
================================================================================

Molecular Symmetry see: T. Pilati & A. Forni, J.Appl.Cryst. (1998), 31, 503-504
For CSM, see: H. Zabrodsky et al. (1993) JACS, 115, 8278-8298

================================================================================
Resd #         Inertial  Moments    Degree Symbol    CSM           RMS    Tol
--------------------------------------------------------------------------------
1      116.      116.      115.    3   Oh       0.0105        0.0102 0.10

Symmetry element     CSM and Max.Diff.  Symmetry element     CSM and Max.Diff.
1 [E  ] x,y,z           0.0000 0.0000   2 [C3 ] y,z,x           0.0042 0.0080
3 [C2 ] -x,-y,z         0.0063 0.0086   4 [C4 ] x,z,-y          0.0105 0.0144
5 [C2 ] x,-y,-z         0.0084 0.0130   6 [C2 ] -x,y,-z         0.0063 0.0086
7 [Cs ] x,y,-z          0.0063 0.0086   8 [Ci ] -x,-y,-z        0.0000 0.0000
9 [C3 ] z,x,y           0.0042 0.0080  10 [C3 ] -y,z,-x         0.0098 0.0125
11 [C2 ] z,-y,x          0.0073 0.0106  12 [C3 ] -y,-z,x         0.0070 0.0121
13 [C3 ] y,-z,-x         0.0070 0.0121  14 [S6 ] y,-z,x          0.0098 0.0125
15 [S6 ] -y,-z,-x        0.0042 0.0080  16 [C3 ] z,-x,-y         0.0070 0.0121
17 [C4 ] -y,x,z          0.0084 0.0129  18 [C3 ] -z,x,-y         0.0070 0.0121
19 [C3 ] -z,-x,y         0.0098 0.0125  20 [S6 ] -z,x,y          0.0070 0.0121
21 [S6 ] -z,-x,-y        0.0042 0.0080  22 [C2 ] -x,-z,-y        0.0000 0.0000
23 [C2 ] -z,-y,-x        0.0031 0.0069  24 [C2 ] -y,-x,-z        0.0031 0.0069
25 [C4 ] -z,y,x          0.0084 0.0129  26 [C2 ] y,x,-z          0.0073 0.0106
27 [C4 ] x,-z,y          0.0105 0.0144  28 [S6 ] -y,z,x          0.0070 0.0121
29 [S6 ] z,x,-y          0.0098 0.0125  30 [Cs ] x,-y,z          0.0063 0.0086
31 [S6 ] y,z,-x          0.0070 0.0121  32 [S6 ] z,-x,y          0.0070 0.0121
33 [Cs ] -x,y,z          0.0084 0.0130  34 [C4 ] y,-x,z          0.0084 0.0129
35 [C2 ] -x,z,y          0.0084 0.0130  36 [C4 ] z,y,-x          0.0084 0.0129
37 [Cs ] x,-z,-y         0.0084 0.0130  38 [S4 ] -z,-y,x         0.0084 0.0129
39 [S4 ] -y,x,-z         0.0084 0.0129  40 [S4 ] -x,z,-y         0.0105 0.0144
41 [S4 ] z,-y,-x         0.0084 0.0129  42 [Cs ] -y,-x,z         0.0073 0.0106
43 [Cs ] z,y,x           0.0031 0.0069  44 [Cs ] y,x,z           0.0031 0.0069
45 [Cs ] x,z,y           0.0000 0.0000  46 [S4 ] y,-x,-z         0.0084 0.0129
47 [S4 ] -x,-z,y         0.0105 0.0144  48 [Cs ] -z,y,-x         0.0073 0.0106
```

2. # Inter-molecular

This (experimental) routine attempts to identify symmetry relations between crystallographically independent molecules.

In general there will be three outcomes of a NONSYM analysis:

1. A symmetry direction is found compatible with the translation lattice. In such a case, ADDSYM should have indicated what the read space group will be.

2. A symmetry direction is found that is not compatible with the translation lattice, i.e with a non-zero angle with all translation vectors in the lattice, and thus only local.
A possible consequence could be disorder/twinning.

3. No satisfactory local or global (pseudo) symmetry direction.

### Instructions

The NONSYM feature is invoked either with a left-button-click on NONSYM or from the keyboard:

CALC NONSYM

SYMMETRY TOOLS PLATON HOMEPAGE
26-Sep-2001 A.L.Spek