Introduction

Introduction to PLATON


PLATON is written by A.L.Spek. It brings together, in the context of a single program, a variety of computational and graphical procedures for the analysis of the results of a crystal structure determination. The program may be used in conjunction with structure determination and refinement programs such as SHELXS and SHELXL. For a discussion of the internal operations in PLATON see how PLATON operates.

PLATON is designed for the automated generation of a variety of geometrical entities such as bond distances, bond angles, torsion angles, least-squares planes and ring-puckering parameters, see an introductory example. All derived parameters are accompanied by standard deviations that are calculated by numerical methods from the supplied standard deviations in the primary input parameters.

The free format input data generally consist of two types of data that are normally but not necessarily supplied separately to the program. The crystallographic or molecular data such as coordinates, thermal parameters, cell dimensions and symmetry, possibly generated by the structure determination or refinement program, are read from an automatically created SPF file. Instructions may entered directly from the keyboard into the PLATON dialog Window (called up from the menu item PLATON command. Alternatively a graphical menu interface (from PLATON menu) is also available.

In general only global instructions are necessary to obtain tables of the required derived molecular geometry data. Specific information such as atomic radii and other properties related with the element types involved are by default drawn from internal tables. The simple instruction CALC will automatically execute virtually all calculations that are of interest for the supplied parameter set.

The set of available analysis procedures includes those for rigid-body thermal motion with bond distance correction, puckering analysis (including the Cremer and Pople variety),hydrogen bonds (including an analysis in terms of networks), voids in the structure and five-coordination (Berry pseudorotation). Appropriate references to the literature are given in the output listing.

The calculations are complemented with graphics facilities such as thermal motion ellipsoid plots, Newman projection plots, space-filling plots and projection plots of the structure on the various least-squares and ring planes.

Note: PLATON is not a finished program. It is constantly improved with new facilities as their need arises in the course of the large variety of structure determinations that are carried out in our laboratory. In view of the extremely large number of options of the program, combined with the unique characteristics of each new crystal structure examined with the program, problems may arise in non-standard cases.

For a recent (2-Feb-98) overview of PLATON click here .