Adaptive-Partitioning Multilayer Dynamics Simulations: 2. Implementations of the Permuted and Interpolated Adaptive-Partitioning Gradients.
Adaptive-Partitioning Multilayer Dynamics Simulations: 2. Implementations of the Permuted and Interpolated Adaptive-Partitioning Gradients.
复制标题
DOI：
10.1021/acs.jpca.3c05600
复制
发表时间：
2023-11
期刊：
影响因子：
--
通讯作者：
Anh L. Tran;Emilie B. Guidez;Hai Lin
中科院分区：
文献类型：
--
作者：
Anh L. Tran;Emilie B. Guidez;Hai Lin
最近，提出了一种自适应划分多层Q1/Q2/MM方法，其中Q1和Q2分别表示两个不同的量子力学理论水平和MM，分子力学力场。这样的多层模型类似于Morokuma及其同事的ONIOM（我们自己的N层集成分子轨道和分子力学）模型，但它的区别在于在动态模拟中将原子重新分类为Q1，Q2或MM。为了平滑地混合原子的描述水平，在相邻层之间引入缓冲区，并且能量被平滑地内插。特别是，Q1/Q2的相互作用能表示在两个不同的形式主义：置换和插值自适应分区（PAP和IAP），分别。虽然PAP能量是基于加权多体展开，但IAP能量是通过使用内插Fock和重叠矩阵的炼金术量子计算得出的。在这篇文章中，我们深入研究了缓冲区和Q2区之间的边界附近的IAP能量的不规则性，这在一些计算中是突出的。这些不规则性是由于基组的线性依赖性，这可以有效地抑制使用加权原子轨道系数的截止。此外，我们推导并实现了PAP和IAP的梯度。一系列的水集群模型的测试计算显示，在PAP完全平滑的梯度，而一个小的不连续性发生在IAP梯度在缓冲区/Q2的边界。当缓冲区/Q2边界进一步远离Q1中心移动时以及当增加所使用的基组的大小时，IAP中的能量和梯度不连续性变得更小。总体而言，这些不连续性是可控的，并讨论了进一步减少它们的可能方法。
Recently, an adaptive-partitioning multilayer Q1/Q2/MM method was proposed, where Q1 and Q2 denote, respectively, two distinct quantum-mechanical levels of theory and MM, the molecular-mechanical force fields. Such a multilayer model resembles the ONIOM (our own N-layered integrated molecular orbital and molecular mechanics) model by Morokuma and co-workers, but it is distinguished by on-the-fly reclassifying atoms to be Q1, Q2, or MM in dynamics simulations. To smoothly blend the levels of descriptions of the atoms, buffer zones are introduced between adjacent layers, and the energy is smoothly interpolated. In particular, the Q1/Q2 interaction energy was expressed in two different formalisms: permuted and interpolated adaptive-partitioning (PAP and IAP), respectively. While the PAP energy is based on a weighted many-body expansion, the IAP energy is derived via alchemical quantum calculations with interpolated Fock and overlap matrices. In this article, we examine in-depth the irregularities in the IAP energy near the boundary between the buffer and Q2 zones, which were found prominent in some calculations. These irregularities are due to basis-set linear dependencies, which can be effectively suppressed using a cutoff for the weighted atomic orbital coefficients. Furthermore, we derived and implemented the gradients for both PAP and IAP. Test calculations on a series of water cluster models show perfectly smooth gradients in PAP, while a minor discontinuity occurs in IAP gradients at the buffer/Q2 boundary. The energy and gradient discontinuities in IAP become smaller when moving the buffer/Q2 boundary further away from the Q1 center and when increasing the size of the basis sets used. Overall, those discontinuities are controllable, and possible ways to further diminish them are discussed.