关键词: 近似从头算, 半正交化, 积分近似, 电荷守恒

Abstract: Kashiwagi used semiorthogonalized orbitals as basis set in quantum chemicalcal culations and proposed a scheme in which two-electron integrals containing orthogonalized orbital pairs were neglected, but the same kind of one-electron integrals were reserved. We proposed in this paper that one-electron integrals containing ortho-gonalized orbital pairs should be neglected too. This improvement makes the calcu-lations more accurate, because nuclear attractive energy is approximately equal to electron repulsive energy in a system. We use simpler orbitals to evaluate threeand four-center integrals, while keeping charge conservation. These two improvements can save a lot of computer time in approximate ab initio calculations.

Key words: Approximate calculation, Semiorthogonalized orbital, Integral approximation, Charge conservation