DIRDIF - ORIENT

ORIENT


ORIENT is a program to find the orientation of a molecular fragment (model) by means of vector search methods (Nordman). The input model is used for the calculation of interatomic vectors. The shape function of a single Patterson peak is approximated from the shape of the origin peak, and it is used for the calculation of the amount of overlap between neighbouring vectors. Vectors are selected on weight (including overlap), length, and mutual separation. A fast cyclic search system, employing increasing resolution per cycle, leads to the best fitting orientation of the model in angular space, i.e. the final result of the program is a set of Eulerian angles (denoted A, B, C) which is applied on the original model. The selection criterion is the Nordman 'minimum average' function value.

The program is used for structures with known geometry for a (relatively small) part of the molecule. Note that such molecular fragment (model) often is available from the users own collection of structure determinations.

When the user calls for ORIENT, the system will automatically arrange for the following calculations: first calculate the Patterson function (programFOUR), then find the orientation of the model (program ORIENT), and continue with translation functions (program TRACOR), and further structure elucidation (programs PHASEX and FOUR).