This manuscript introduces a methodology (within the Born-Oppenheimer picture) to compute electronic ground-state properties of molecules and solids/surfaces with fractionally occupied components. Given a user-defined division of the molecule into subsystems, our theory uses an auxiliary global Hamiltonian that is defined as the sum of subsystem Hamiltonians, plus the spatial integral of a second-quantized local operator that allows the electrons to be transferred between subsystems. This electron transfer operator depends on a local potential that can be determined using density functional approximations and/or other techniques such as machine learning. The present framework employs superpositions of tensor-product wave functions, which can satisfy size consistency and avoid spurious fractional charges at large bond distances. The electronic population of each subsystem is in general a positive real number and is obtained from wave-function amplitudes, which are calculated by means of ground-state matrix diagonalization (or matrix propagation in the time-dependent case). Our method can provide pathways to explore charge-transfer effects in environments where dividing the molecule into subsystems is convenient and to develop computationally affordable electronic structure algorithms.

中文翻译：

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本地耦合开放子系统：形式化的价格合理的电子结构计算，具有分数电荷和尺寸一致性

该手稿介绍了一种方法（在Born-Oppenheimer图片内），用于计算分子和具有部分占据组分的固体/表面的电子基态性质。给定用户将分子划分为子系统的方式，我们的理论使用了辅助全局哈密顿量，其定义为子系统哈密顿量的总和，再加上第二数量化的局部算子的空间积分，该空间算符允许电子在子系统之间转移。该电子转移算子取决于可以使用密度泛函近似和/或其他技术（例如机器学习）确定的局部电势。本框架采用张量积波函数的叠加，可以满足尺寸一致性并避免在大键距处出现伪分数电荷。每个子系统的电子总数通常为正实数，并且是通过波函数振幅获得的，这些波函数振幅是通过基态矩阵对角化（或在与时间有关的情况下矩阵传播）来计算的。我们的方法可以为探索将分子划分为子系统的环境中的电荷转移效应提供便利的途径，并开发出计算上可承受的电子结构算法。