Quantum mechanical treatment of molecules. Part 5.—Calculations of the potential energy curve and molecular constants of LiH (X1∑+)

Abstract

The self-consistent field molecular orbital (S.C.F. M.O.) method in the linear combination of atomic orbitals (L.C.A.O.) approximation is applied to the ground state of LiH (X¹∑⁺) at a number of internuclear distances R for the calculation of the potential energy (P.E.) curve and molecular constants. In this calculation both the L.C.A.O. coefficients and the screening constants of 1s, 2s, 2p_z, 3s, 3p_z A.O. of Li and 1s, 2s, 2p_z A.O. of H are optimized. Another calculation with an extended basis set, involving the optimized exponents of the above A.O. and some estimated exponents for the higher A.O., was carried out and subjected to a configuration interaction treatment at a number of R to obtain a P.E. curve. The P.E. curves, computed with and without configuration interaction treatment, have been used in the solution of the radial Schrödinger equation to compute the molecular constants ω_e, ω_ex_e, B_e, α_e, R_e and D_e. The computed results are compared with those calculated with a limited set of optimized basis functions and those reported by others² and the experimental data.²