ELECTRONIC LONE-PAIR LOCALIZATION AND ELECTROSTATIC ENERGY CALCULATIONS - APPLICATION TO ALPHA-PBO, SNO, PB-1-X(TIO)(X)O, PB3O4,PB-3(V,P)(2)O-8, AND A BISRCACUO-TYPE SUPERCONDUCTOR

A method of calculation has been developed far localizing electronic lone pairs in crystalline structures including incommensurate modulated structures or structures containing impurities. The cohesion energy of the resulting structure (ions and lone pairs) may also be calculated. The calculation is based on the method of A. Verbaere, R. Marchand, and M. Tournoux (J. Solid State Chem. 23, 383, 1978), which assumes knowledge of the electronic polarizability coefficient of the ions possessing a lone pair, relative to the local electric field in the crystalline structure. These calculations have been made for some compounds and related to experimental studies. The influence of the lone pairs on the structural incommensurate transition of alpha-PbO is studied and compared with their influence on the structural evolution of SnO and Pb-1-x(TiO)(x)O. Using the same method, the role of the lone pairs in Pb3O4, Pb-3(V,P)(2)O-8, and a BiSrCaCuO-type incommensurate superconductor is discussed. (C) 1995 Academic Press, Inc.