Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi, 444-8585, Japan.
J Chem Phys. 2012 Mar 28;136(12):124106. doi: 10.1063/1.3696962.
We present an orbital-optimized version of our orbital-specific-virtuals second-order Møller-Plesset perturbation theory (OSV-MP2). The OSV model is a local correlation ansatz with a small basis of virtual functions for each occupied orbital. It is related to the Pulay-Saebø approach, in which domains of virtual orbitals are drawn from a single set of projected atomic orbitals; but here the virtual functions associated with a particular occupied orbital are specifically tailored to the correlation effects in which that orbital participates. In this study, the shapes of the OSVs are optimized simultaneously with the OSV-MP2 amplitudes by minimizing the Hylleraas functional or approximations to it. It is found that optimized OSVs are considerably more accurate than the OSVs obtained through singular value decomposition of diagonal blocks of MP2 amplitudes, as used in our earlier work. Orbital-optimized OSV-MP2 recovers smooth potential energy surfaces regardless of the number of virtuals. Full optimization is still computationally demanding, but orbital optimization in a diagonal or Kapuy-type MP2 approximation provides an attractive scheme for determining accurate OSVs.
我们提出了一种轨道优化版本的轨道特定虚拟二阶 Møller-Plesset 微扰理论（OSV-MP2）。OSV 模型是一种局部相关假设，每个占据轨道都有一个小的虚拟函数基。它与 Pulay-Saebø 方法有关，其中虚拟轨道的域是从一组投影原子轨道中提取的；但在这里，与特定占据轨道相关联的虚拟函数是专门针对该轨道参与的相关效应进行调整的。在这项研究中，通过最小化 Hylleraas 泛函或其近似值，同时对 OSV-MP2 振幅进行优化。结果发现，与我们早期工作中使用的通过对角块的奇异值分解获得的 OSV 相比，优化后的 OSV 更为准确。轨道优化的 OSV-MP2 无论虚拟轨道的数量如何，都能恢复平滑的势能表面。完全优化仍然需要大量的计算资源，但对角或 Kapuy 型 MP2 近似的轨道优化为确定准确的 OSV 提供了一种有吸引力的方案。
