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THE NEED FOR REALISTIC ELECTROSTATIC MODELS TO PREDICT THE CRYSTAL-STRUCTURES OF NLO MOLECULES

WILLOCK, DJ; LESLIE, M; PRICE, SL; CATLOW, CRA; (1993) THE NEED FOR REALISTIC ELECTROSTATIC MODELS TO PREDICT THE CRYSTAL-STRUCTURES OF NLO MOLECULES. In: MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS. (pp. 499 - 506). GORDON BREACH SCI PUBL LTD

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Abstract

Organic molecules with high non-linear optic coefficients have polar groups often linked by delocalised pi-electron systems. Thus the charge distribution around many atoms in such molecules will be highly non-spherical. Current methods of predicting the crystal structures of these molecules, and thus the macroscopic second harmonic generation capability, take no account of these features as they use fixed charges at each atomic site to model the electrostatic interaction.A more realistic representation of the electrostatic interaction is to use a set of multipole moments on each atom, which may be derived from a distributed multipole analysis of an ab-initio wavefunction for the isolated molecule. We have adapted the widely used THBREL program to simulate the crystal packing of organic molecules, using the distributed multipole electrostatic model.Preliminary results for the prediction of the crystal structures of molecules such as meta-nitroaniline are presented and contrasted with an atomic point charge model. The electrostatic effects of the lone pair and pi-electron density makes a qualitative difference to the crystal packing.

Type:Proceedings paper
Title:THE NEED FOR REALISTIC ELECTROSTATIC MODELS TO PREDICT THE CRYSTAL-STRUCTURES OF NLO MOLECULES
Event:1st European Conference on Molecular Electronics ( ECME 92 ) / 1992 Annual Joint Meeting of the European-Physical-Chemistry-Divisions/Associations
Location:PADUA, ITALY
Dates:1992-08-24 - 1992-08-28
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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