Ab initio calculation of force constants and equilibrium geometries in polyatomic molecules

作者：Péter Pulay · 发表于：Molecular Physics · 年份：1969 · DOI：10.1080/00268976900100941 · 被引用次数：2392 · 研究领域：Cold Atom Physics and Bose-Einstein Condensates、Quantum, superfluid, helium dynamics、Advanced Chemical Physics Studies

The general expression for the exact forces on the nuclei (negative derivatives of the total energy with respect to the nuclear coordinates) is applied for Hartree-Fock wavefunctions. It is suggested that force constants should be calculated by differentiating the forces numerically. This method, called the force method, is numerically more accurate and requires less computation than the customary one of differentiating the energy numerically twice. It permits the quick determination of the equilibrium geometry by relaxing the nuclear coordinates until the forces vanish. The unreliability of the methods using the Hellmann-Feynman forces is re-emphasized. The question of which force constants can be best calculated ab initio is discussed.