Fragment-Based Direct-Local-Ring-Coupled-Cluster Doubles Treatment Embedded in the Periodic Hartree-Fock Solution.
Fragment-Based Direct-Local-Ring-Coupled-Cluster Doubles Treatment Embedded in the Periodic Hartree-Fock Solution.
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DOI：
10.1021/acs.jctc.6b00651
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发表时间：
2016-09
影响因子：
5.5
通讯作者：
O. Masur;M. Schütz;L. Maschio;D. Usvyat
中科院分区：
文献类型：
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作者：
O. Masur;M. Schütz;L. Maschio;D. Usvyat
我们提出了一个周期/有限团簇界面，用于嵌入在周期平均场中的基于碎片的直接局部环耦合团簇双星(d-LrCCD)计算。该片段由一组Wannier函数(WF)定义，该Wannier函数集是通过周期性的Hartree-Fock计算获得的。对特定的虚拟空间由截断到对区域的投影原子轨道(PAO)来跨越。计算过程由周期性的局部M&Plesset(LMP2)计算启动。WF对的一个子集随后使用Molpro的局部耦合簇程序进行有限簇d-LrCCD处理；这个子集由轨道间截止距离指定。D-LrCD所需的轨道、对和磁区列表以及其他必要的量，如Fock矩阵和重叠矩阵，以及基于WFS和PAO的电子排斥积分(ERI)在周期框架中被评估，并通过接口传递给Molpro。这些周期量为片段d-LrCCD提供了正确的周期平均场嵌入。此外，不需要涉及与大支持星系团相关的轨道系数的昂贵的轨道变换。出现在d-LrCCD图中的误差因式通过密度拟合被分解，这使得能够通过三指数中间体有效地处理相应的项。还计算了相应的3指标和涉及辅助函数的度量2指标ERI，并将其转换为周期侧的WF-PAO基(3指标ERI)。虽然直接环-CCD方法本身并不比MP2方法更精确，但它在小带隙系统中更稳定，因为它将环图归结到无限量级。此外，该界面是迈向高水平基于片段的量子化学处理的第一步，例如在较低水平处理的周期性嵌入内的局部CCSD(T)。作为两个实验例子，我们研究了H2和Ar在石墨烷上的物理吸附。
We present a periodic/finite-cluster interface for fragment-based direct local ring-coupled-cluster doubles (d-LrCCD) calculations embedded in the periodic mean field. The fragment is defined by a set of Wannier functions (WFs), obtained from a periodic Hartree-Fock calculation. The pair-specific virtual space is spanned by projected atomic orbitals (PAOs) truncated to pair domains. The computational procedure is initiated by a periodic local Møller-Plesset (LMP2) calculation. A subset of the WF pairs is then subsequently subjected to a finite-cluster d-LrCCD treatment using the local coupled cluster program of Molpro; this subset is specified by an interorbital cutoff distance. The orbital, pair, and domain lists, as well as other essential quantities needed for d-LrCCD such as the Fock and overlap matrices, and the electron repulsion integrals (ERIs) in the basis of WFs and PAOs are evaluated in the periodic framework and passed to Molpro via an interface. These periodic quantities provide the correct periodic mean-field embedding for the fragment d-LrCCD. Moreover, no expensive orbital transformations involving orbital coefficients related to large supporting clusters are necessary. ERIs appearing in the d-LrCCD diagrams are factorized via density fitting, which enables an efficient processing of the corresponding terms via three-index intermediates. The corresponding 3-index and the metric 2-index ERIs involving auxiliary functions are also computed and transformed to the WF-PAO basis (the 3-index ERI) on the periodic side. Although the direct ring-CCD method itself is not generally more accurate than MP2, it is more stable in the case of small band gap systems, as it sums up the ring diagrams to infinite order. Furthermore, this interface is a first step toward a high-level fragment-based quantum chemical treatment such as local CCSD(T) within a periodic embedding that is treated at a lower level. As two test examples we study the physisorption of H2 and argon on graphane.