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首页> 外文期刊>The Journal of Chemical Physics >Analytic energy derivatives for the calculation of the first-order molecular properties using the domain-based local pair-natural orbital coupled-cluster theory
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Analytic energy derivatives for the calculation of the first-order molecular properties using the domain-based local pair-natural orbital coupled-cluster theory

机译：使用基于域的局部对-自然轨道耦合簇理论计算一级分子性质的解析能量导数

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The domain-based local pair-natural orbital coupled-cluster (DLPNO-CC) theory has recently emerged as an efficient and powerful quantum-chemical method for the calculation of energies of molecules comprised of several hundred atoms. It has been demonstrated that the DLPNO-CC approach attains the accuracy of a standard canonical coupled-cluster calculation to about 99.9% of the basis set correlation energy while realizing linear scaling of the computational cost with respect to system size. This is achieved by combining (a) localized occupied orbitals, (b) large virtual orbital correlation domains spanned by the projected atomic orbitals (PAOs), and (c) compaction of the virtual space through a truncated pair natural orbital (PNO) basis. In this paper, we report on the implementation of an analytic scheme for the calculation of the first derivatives of the DLPNO-CC energy for basis set independent perturbations within the singles and doubles approximation (DLPNO-CCSD) for closed-shell molecules. Perturbation-independent one-particle density matrices have been implemented in order to account for the response of the CC wave function to the external perturbation. Orbital-relaxation effects due to external perturbation are not taken into account in the current implementation. We investigate in detail the dependence of the computed first-order electrical properties (e.g., dipole moment) on the three major truncation parameters used in a DLPNO-CC calculation, namely, the natural orbital occupation number cutoff used for the construction of the PNOs, the weak electron-pair cutoff, and the domain size cutoff. No additional truncation parameter has been introduced for property calculation. We present benchmark calculations on dipole moments for a set of 10 molecules consisting of 20-40 atoms. We demonstrate that 98%-99% accuracy relative to the canonical CCSD results can be consistently achieved in these calculations. However, this comes with the price of tightening the threshold for the natural orbital occupation number cutoff by an order of magnitude compared to the DLPNO-CCSD energy calculations. Published by AIP Publishing.
机译：基于域的局部对-自然轨道耦合簇（DLPNO-CC）理论最近成为一种有效而强大的量子化学方法，用于计算由数百个原子组成的分子的能量。业已证明，DLPNO-CC方法可实现标准规范耦合聚类计算的精度达到基集相关能量的约99.9％，同时实现相对于系统尺寸的计算成本的线性缩放。这是通过组合（a）局部占据的轨道，（b）由投影原子轨道（PAO）跨越的大型虚拟轨道相关域以及（c）通过平截对自然轨道（PNO）压缩虚拟空间来实现的。在本文中，我们报告了一种解析方案的实现，该方案用于计算DLPNO-CC能量的一阶导数，用于封闭壳分子的单双近似法（DLPNO-CCSD）内的基集独立扰动。为了解决CC波函数对外部扰动的响应，已经实现了与扰动无关的单粒子密度矩阵。在当前的实现中，没有考虑由于外部扰动引起的轨道松弛效应。我们详细研究了计算出的一阶电学性质（例如，偶极矩）对DLPNO-CC计算中使用的三个主要截断参数（即用于构造PNO的自然轨道占据数截止）的依赖性，弱电子对截止和畴尺寸截止。尚未引入用于属性计算的其他截断参数。我们介绍了由20-40个原子组成的10个分子的偶极矩的基准计算。我们证明相对于规范的CCSD结果，可以在这些计算中始终达到98％-99％的精度。但是，与DLPNO-CCSD能量计算相比，将自然轨道占用数截止的阈值提高一个数量级的代价是随之而来的。由AIP Publishing发布。

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