BONDING FEATURES OF LIH - A VBSCF STUDY

A quantitative description of the bonding features of LiH based on VBS CF method and 6-311G* basis set is reported. The calculations include three (sigma type) or six (sigma + pi type) resonance structures. The optimized geometries of the ground and the first excited states are c ompared with experimental and other theoretical studies. The energies resulted from 3BTSCF and 6BTSCF around the equilibrium position are ra ther near to those obtained from MP2 calculations. Analyses show that the bond of LiH is chiefly covalent instead of ionic. At the equilibri um distances of the ground state (R = 3.105 au with 3BTSCF) and the fi rst excited state (R = 4.589 au with 3BTSCF), the structural weights o f the covalent function are 0.89 and 0.93, respectively. Subsequently the exceptionally high dipole moment of LiH is dominantly due to the p olarization or hybridization of the atomic orbitals on Li. A VB explan ation for the dipole moment curve of the first excited state is also p resented.