ADDSYM + PLOT

SYMMETRY TOOLS PLATON HOMEPAGE

Same as ADDSYM + transformation & Plot of averaged structure in revised space group.

Example #1 : Cubic structure published as Orthorhombic

Following is an example ( ex3.spf) taken from the Cambridge Crystallographic Database of a structure published in the orthorhombic space group Pbca with one molecule in the asymmetric unit which transforms easily to the cubic space group Pa-3.

The structure in the orthorhombic description looks as shown in Fig1.

Either by clicking on 'ADDSYM-PLT' or with the keyboard instruction CALC ADDSYM PLOT it will be shown by PLATON/ADDSYM that a better description of the structure in the cubic space group Pa-3 is possible (Fig2) with only 1/3 of the molecule in the asymmetric unit.

The non-conforming hydrogen atoms on the methyl moiety are either disordered or misplaced in the original model.

Example #2: Find symmetry in 'calculated structure'

This example model.spf starts out from a calculated structure of Dioxane molecules in spacegroup P1 (Note the unusual (non-standard) beta angle of 19.2 degrees).

ADDSYM will detect an I-centering first. This lattice centering type is implemented, along with the detected inversion center, and ADDSYM restarted automatically using this information. The analysis shows that the coordinate set can be simplified by in description of the structure in space group C2/m.

A CALC ADDSYM PLOT will thus result in a description of the structure in spacegroup C2/m as shown in Fig.3.

SYMMETRY TOOLS PLATON HOMEPAGE
09-feb-2000 A.L.Spek