Some practical aspects of the use of the new types of discrepancy factors in crystal structure refinement

Abstract

The relationship between the errors in the atomic coordinates and the values of the new discrepancy factors proposed by Srinivasan and Srikrishnan is worked out. This is done for the general case when only a part of the structure is used in the calculated structure factors and these have finite errors in their coordinates. The results are verified using hypothetical models both for the centrosymmetric and the non-centrosymmetric cases. Practical aspects of using these indices for the estimation of the mean error in the atomic coordinates are discussed and the necessary graphs are given. The theoretical results enable us to make a comparison of the new discrepancy index with the conventional one and it leads us to conclude that theoretically the new indices might prove to be more sensitive towards final stages of crystal-structure refinement.