Models of atomic electric multipoles for the water molecule have been optimized in order to reproduce the electric potential around the molecule computed by ab initio calculations at the coupled cluster level of theory with up to noniterative triple excitations in an augmented triple-zeta quality basis set. Different models of increasing complexity, from atomic charges up to models containing atomic charges, dipoles, and quadrupoles, have been obtained. The geometry dependence of these atomic multipole models has been investigated by changing bond lengths and HOH angle to generate 125 molecular structures (reduced to 75 symmetry-unique ones). For several models, the atomic multipole components have been fitted as a function of the geometry by a Taylor series of fourth order in monomer coordinate displacements.

中文翻译：

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水分子的几何相关原子多极模型

已优化水分子的原子电多极模型，以便重现通过分子耦合理论从头算计算，从头算计算得到的分子周围的电势，并在增强的三重ζ质量基础集中进行多达三重的非迭代三重激发。已经获得了越来越复杂的不同模型，从原子电荷到包含原子电荷，偶极子和四极子的模型。这些原子多极模型的几何相关性已通过改变键长和HOH角以生成125个分子结构（减少为75个对称唯一结构）进行了研究。对于几种模型，原子多极组件已根据几何形状通过单体坐标位移中的四阶泰勒级数进行拟合。