SCF Ab initio studies of infinite systems and molecular aggregates

Abstract

The pseudo-lattice(PL) method has been reformulated for ab initio self-consistent-field(SCF) calculations. The translational symmetries of infinite systems have been applied to the finite model chain by manipulating all the intramolecular and intermolecular Fock matrices. The nuclear repulsion energy has been corrected accordingly. The method has been tested for the linear chain of lithium hydride under the constraint of equidistance between all neighboring lithium and hydrogen atoms. The calculated results of the infinite chain have been compared with those of finite chains of lithium hydride under the same geometric constraint. The equilibrium geometries, band structures, intermolecular stabilization energies, and potential curves have been studied. It has been found that the infinite systems cannot be described by considering only first nearest neighbor interactions, and the intermolecular interactions must be considered at least up to third nearest neighbors in order to obtain accurate value of force constant of infinite systems. We can conclude from band structures of infinite chains that the boundary effect of the finite model chain is effectively removed by the PL method. In addition, we have investigated about the points of similarities and differences between lithium and hydrogen bonds which are known as good objectives for studying intermolecular interactions of electron donor-acceptor type. SCF and post SCF methods were employed to study the equilibrium structures, energies, and charge transfer appearences. The structures of lithium bonded complexes were observed to be quite linear. Accordingly, dipole moments of lithium bonded complexes were found to be increased. Lithium atoms in lithium bonded complexes were more shared by two groups of both directions than hydrogen atoms in hydrogen bonded complexes. Intermolecular interaction energies of lithium bonded complexes were found to be much greater than those of hydrogen bonded complexes. The direction...