四次方程
原子轨道
振幅
功能(生物学)
基质(化学分析)
物理
量子力学
化学
数学
电子
色谱法
进化生物学
生物
纯数学
作者
Michael J. Frisch,Martin Head‐Gordon,John A. Pople
标识
DOI:10.1016/0009-2614(90)80029-d
摘要
We present a direct method for evaluating the gradient of the second-order Møller-Plesset (MP2) energy without storing any quartic quantities, such as two-electron repulsion integrals (ERIs), double substitution amplitudes or the two-particle density matrix. For an N-basis-function calculation, N3 memory is required, and the ERIs and their first derivatives are computed up to O (number of occupied orbitals) times, plus additional ERI evaluations to obtain the Hartree-Fock (HF) orbitals and solve the coupled perturbed HF equation. Larger amounts of memory are used to reduce the O evaluations in the MP2 step. The floating point operation count is still proportional to ON4, as in conventional MP2 gradient codes since ERI evaluation is just an N4 step. Illustrative calculations are reported to assess the performance of the algorithm.
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