Finite basis vibrational configuration interaction theory (VCI) is a highly accurate method for the variational calculation of state energies and related properties, but suffers from fast growing computational costs in dependence of the size of the correlation space. In this series of papers, concepts and techniques will be presented, which diminish the computational demands and thus broaden the applicability of this method to larger molecules or more complex situations. This first part focuses on a highly efficient implementation of the vibrational angular momentum (VAM) terms as occurring in the Watson Hamiltonian and the prediagonalization of initial subspaces within an iterative configuration selective VCI implementation. Working equations and benchmark calculations are provided, the latter demonstrating the increased performance of the new algorithm.

中文翻译：

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振动构型相互作用理论的进展 - 第 1 部分：振动角动量项的有效计算

有限基振动构型相互作用理论 (VCI) 是一种用于状态能量和相关属性变分计算的高精度方法，但由于相关空间的大小而导致计算成本快速增长。在本系列论文中，将介绍概念和技术，它们减少了计算需求，从而扩大了该方法对更大分子或更复杂情况的适用性。第一部分重点介绍在 Watson Hamiltonian 中出现的振动角动量 (VAM) 项的高效实现以及迭代配置选择性 VCI 实现中初始子空间的预对角化。提供工作方程和基准计算，