Evaluation of EFG parameters in XO −3 ions (XCl,Br,I) by CNDO/2 and indo methods

Abstract

One can not apply the conventional point charge model to evaluate the EFG parameters at the halogen site in chlorates, bromates and iodates since, in XO − 3 ions (XCl,Br,I), the halogen atom is covalently bonded to the oxygens of the group and the effect of the cation on EFG is negligible. Therefore molecular orbital calculations by both CNDO/2 and INDO methods have been attempted to evaluate the EFG parameters. The currently available program (ref.1) for CNDO/2 and INDO methods has been extended to III and IV row elements using Hase and Schweig (ref.2) and Deb and Coulson (ref.3) parameters. The EFG parameters obtained from population density matrix (ref.4) from these two methods have been compared with the experimental data wherever available. It has been concluded that CNDO/2 method is better suited for the determination of EFG parameters in XO − 3 ions compared to INDO method. The reason for this is discussed.