First-Principles Study of the Nature of Binding in BF$_{3}$ Molecular Solids

The binding of BF$_{3}$ molecules in solid BF$_{3}$ is studied by the Hartree-Fock Cluster Procedure, with Van der Waals interaction between the BF$_{3}$ molecules included by the many-body perturbation theory procedure. The binding appears to be the result of strong cancellation between one-electron effects, represented by the covalent interaction between neighboring molecules combined with the coulomb interaction between the effective charges on the boron and fluorines in each of the neutral BF$_{3}$ molecules and the many-body correlation effect between electrons on neighboring molecules leading to the Van der Waals interaction, the latter being the determining factor for the binding. Quantitative results will be presented for the binding energy in this solid state system which represents a class of molecular solids for which the neutral molecular units have substantial effective charges of different signs on the constituent atoms.$_{ }$