Lattice Dynamics and Structural Instabilities in Biphenyl Sulfone Derivatives

概要

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Bis(4-chlorophenyl)strlfone (BCIPS) is one of the few orgttnic rno[ecvrlar solids ',vlxich exhibits adisplacive norttaal-incotmtt?ensurate phase tr'arnsition involving spatr;tl rnoc1vxl?ttxons of conforxaaational parauneters. In the present work, the rootm tetnperattrre Pll21SC of BCIPS W'LXS takerx LXS aprototype, in order to investigate the strtrcturatl stability of' a group of' ret?rted solids. Latticedynamics calculatiorts were performed in order to detect j.>ossil*le sof't mode inst?tbilities in thephonon dispersion branches. An atotaaistic setnietaapirical ajcpro?tch was adopted in lattice calcu-Nations, in addition to a semirigid molectrlarr naodel considering the possiT.oility of cotrjcling betweenlattice and low lying internal degrees of ['reedotaa. Also, free-tnolectnle equilibriutaa strtncture arnddynamics calculations were perf'orzaaed trsing ?tb initio 3-2lG' unethods, to evaluate the extentof conforrnational distortions of the nuolecule izt solid Pl12lS6. The contribtrtion of tlae internalpotential and the rnolectrlar packing on the l?tttice ir?stability of' BCIPS ;rnd related derivativesare discussed. The restrlts stmggest that a possible new gI0L1J) of' trnstaxble molectrl?tr solids witha COIIIIIIOII prototype packing at high tetaaperatture could be identified, in a sittration resenablingthe A2BX4 fanaily of ionic solids.
社団法人日本物理学会の論文
1999-02-15