Transition probability approach for direct calculation of coefficients of configuration interaction wave function

摘要

To reduce the computation cost of configuration interaction (CI) method, a novel technique is used to calculate the coefficients of doubly excited determinants directly from orbital energies, orbital overlap matrix and electron population obtained from Hartree-Fock level run. This approach to approximate the coefficients of CI wave function is termed as transition probability approximated CI (TPA-CI). In principle, calculated dynamical electron correlation energies of TPA-CI and full CI (FCI) are equivalent. It is observed that computed TPA-CI correlation energies of hydrogen, water, ammonia and ozone are close to the FCI values, within 5% error. The potential energy curve of hydrogen molecule is also studied, and it is found that the energy is minimum at its equilibrium bond length.