通过非正交组态相互作用达到完全相关：二阶微扰方法
Reaching Full Correlation through Nonorthogonal Configuration Interaction: A Second-Order Perturbative Approach
摘要：
非正交多参考方法可以预测静态相关的绝热能量，同时通过非绝热参考态的组合提供化学见解。然而，使用非正交多参考展开达到定量准确性仍然是一个重大的挑战。在这项工作中，我们首次对非正交配置相互作用进行了严格的微扰修正，从而可以可靠地计算剩余的动态相关性。我们的二阶“NOCI-PT 2”理论利用零阶广义Fock哈密顿量，并建立了一阶相互作用空间，使用单，双激发每个参考行列式。因此，这种方法定义了严格的非正交扩展到传统的多参考微扰理论。我们发现，NOCI-PT 2可以定量预测多参考势能面，并提供特定的基态和激发态绝热避免交叉。此外，我们引入了一个明确的mixary移位形式主义，需要的移位值是一个数量级小于传统的多参考微扰理论中使用的。
英文摘要：
Nonorthogonal multireference methods can predict statically correlated adiabatic energies while providing chemical insight through the combination of diabatic reference states. However, reaching quantitative accuracy using nonorthogonal multireference expansions remains a significant challenge. In this work, we present the first rigorous perturbative correction to nonorthogonal configuration interaction, allowing the remaining dynamic correlation to be reliably computed. Our second-order "NOCI-PT2" theory exploits a zeroth-order generalised Fock Hamiltonian and builds the first-order interacting space using single and double excitations from each reference determinant. This approach therefore defines the rigorous nonorthogonal extension to conventional multireference perturbation theory. We find that NOCI-PT2 can quantitatively predict multireference potential energy surfaces and provides state-specific ground and excited states for adiabatic avoided crossings. Furthermore, we introduce an explicit imaginary-shift formalism requiring shift values that are an order of magnitude smaller than those used in conventional multireference perturbation theory.
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