Solids modeled by ab initio crystal field methods. Part 20. Charge transfer in white form of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate

For the white form of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate the geometry has been optimized at the ab initio Hartree-Fock level using a supermolecule model. For each of the two different molecules (A and B) present in the unit cell a separate supermolecular cluster has been built, containing both A- and B-type molecules. The structure of the white form of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate was considered to be optimized when both clusters were refined. The central part of each cluster includes a central molecule and its 14 nearest neighboring molecules described by a wave function. This central part is surrounded by other molecules represented by point charges placed at the atomic positions. The radius of a complete cluster is approximately 30 Angstrom. Because the mutual hydrogen bond interactions between A- and B-type molecules are different, a charge transfer of 0.03e has been calculated between the two molecules using this ab initio crystal field method. (C) 2001 Elsevier Science B.V. All rights reserved.