Calculation of harmonic force constants from Hartree-Fock-Roothaan wavefunctions

Some current methods of non-empirical computation of force constants are discussed; emphasis is given to the complete, analytical evaluation. It is shown that force constants evaluated to the Hartree-Fock limit are correct through first order in the error of the wavefunction. The consequences of using well-optimized wavefunctions are investigated in some detail. Some of the aspects are illustrated by exploratory calculations on H 2 .