Cumulative atomic multipole moments for molecular crystals fromab-initio crystal orbital wave functions and for molecules in excited states fromab-initio MRD-CI wave functions

Abstract

Compact representation of molecular charge distribution in molecular crystals has been derived from ab-initio crystal orbital wavefunction within the framework of cumulative atomic multipole moment (CAMM) expansion. Results for HF, COz, and cubane C8H8 crystals have been compared with values calculated for corresponding clusters within conventional LCAO MO SCF approach. CAMM technique has also been used to represent molecular charge distribution in electronic excited states using CI wavefunction obtained from multireference configuration interaction ( MRD-CI) calculations. This approach supplements previously introduced uncorrelated and correlated CAMM'S and allows accurate nonempirical modeling of electrostatic effects involving molecules in excited states or in crystalline environment. Improved point charge model derived from CAMM has been also described.