【摘要】 介绍了从单Hartree-Fock 行列式出发计算电子相关能的一种普遍方法,即在组态系数中引入二次项,用修改后的组态相互作用理论方程,计算所得的总能量仍具有大小一致性。当采用截断为单和双取代的组态空间,得到这套易于处理的二次方程被称之为QCISD法。还讨论了QCISD法和耦合簇理论之间的关系,概述了增加三级取代校正的一种简化方法QCISD(T)。更多还原

【Abstract】 A general procedure is introduced for calculation of the electron correlation energy, begining from a single Hartree-Fock determinant. The normal equations of configuration interaction theory are modified by introducing new terms which are quadratic in the configuration coefficients and which ensure size consistency in the resulting total energy. When used in the the truncated configuration space of single and double substitutions,the method termed QCISD,leads to a tractable set of quadratic equations.The relation of this method to coupled-cluster (CCSD) is discussed.A simplified method of adding corrections for triple substitutions is outlined,leading to a method termed QCISD(T).更多还原