Analytical gradients for projection-based wavefunction-in-DFT embedding
Analytical gradients for projection-based wavefunction-in-DFT embedding
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DOI：
10.1063/1.5109882
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发表时间：
2019-03
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通讯作者：
Sebastian J. R. Lee;Feizhi Ding;F. Manby;Thomas F. Miller
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文献类型：
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作者：
Sebastian J. R. Lee;Feizhi Ding;F. Manby;Thomas F. Miller
基于投影的嵌入提供了一种简单、稳健且准确的方法，用于在相关波函数 (WF) 方法的水平上描述化学系统的一小部分，而系统的其余部分则在密度泛函理论 (DFT) 的水平上进行描述。在这里，我们提出了基于投影的波函数密度泛函理论（WF-in-DFT）嵌入的解析核梯度的推导、实现和数值演示。梯度在拉格朗日框架中制定，以强制分子轨道的正交性、局域化和布里渊约束。梯度理论的一个重要方面是，可以使用现有的 WF 梯度实现来简单地评估 WF 对总 WF-in-DFT 梯度的贡献，而无需修改。另一个简化的方面是 Kohn-Sham (KS) DFT 对基于投影的嵌入梯度的贡献不需要了解超出宽松 WF 密度的 WF 计算知识。因此，基于投影的 WF-in-DFT 嵌入梯度很容易推广到 WF 和 KS-DFT 方法的任何组合。我们对该方法的多种应用进行了数值演示，包括在耦合簇单双 DFT 理论水平上使用微动弹性带方法计算钴基分子催化剂中氢化物转移的最小能量路径，这揭示了与使用 DFT 预测的过渡态几何结构的巨大差异。
Projection-based embedding provides a simple, robust, and accurate approach for describing a small part of a chemical system at the level of a correlated wavefunction (WF) method, while the remainder of the system is described at the level of density functional theory (DFT). Here, we present the derivation, implementation, and numerical demonstration of analytical nuclear gradients for projection-based wavefunction-in-density functional theory (WF-in-DFT) embedding. The gradients are formulated in the Lagrangian framework to enforce orthogonality, localization, and Brillouin constraints on the molecular orbitals. An important aspect of the gradient theory is that WF contributions to the total WF-in-DFT gradient can be simply evaluated using existing WF gradient implementations without modification. Another simplifying aspect is that Kohn-Sham (KS) DFT contributions to the projection-based embedding gradient do not require knowledge of the WF calculation beyond the relaxed WF density. Projection-based WF-in-DFT embedding gradients are thus easily generalized to any combination of WF and KS-DFT methods. We provide a numerical demonstration of the method for several applications, including a calculation of a minimum energy pathway for a hydride transfer in a cobalt-based molecular catalyst using the nudged-elastic-band method at the coupled-cluster single double-in-DFT level of theory, which reveals large differences from the transition state geometry predicted using DFT.