Guided Diffusion Monte Carlo: A Method for Studying Molecules and Ions That Display Large Amplitude Vibrational Motions
Guided Diffusion Monte Carlo: A Method for Studying Molecules and Ions That Display Large Amplitude Vibrational Motions
复制标题
引导扩散蒙特卡罗：一种研究显示大振幅振动的分子和离子的方法
DOI：
10.1021/acs.jpca.0c07181
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
McCoy, Anne B.
中科院分区：
文献类型：
--
作者：
Finney, Jacob M.;DiRisio, Ryan J.;McCoy, Anne B.
扩散蒙特卡罗方法为基于势能面的分子体系基态性质的计算提供了一种有效的途径。该方法已被证明需要越来越大的合奏时，内和分子间的振动弱耦合。我们最近提出了一种指导性的扩散蒙特卡罗方法，以解决水团簇的这些挑战[Lee，V.G. M.;麦考伊，A. B.J.Phys.Chem.A2019，123，8063 - 8070]。在本研究中，我们扩展了这种方法，并将其应用到更强的结合分子离子，特别是CH 5+和H+（H2O）n=1-4。对于质子化的水系统，我们表明，指导DMC的方法，开发的研究（H2O）n可以用来描述的OH拉伸和HOH弯曲的溶剂化水分子，以及自由OH拉伸水合氢核心。对于H ~+（H_2O）的H_3O ~+核心中的氢键OH伸缩与CH ~（5+）中的CH伸缩，我们根据感兴趣离子的瞬时结构发展了自适应引导函数。使用这些指导功能，我们表明，我们能够获得收敛的零点能量和基态波函数使用合奏大小是小到10%的大小，需要获得类似的精度从非指导计算。
Diffusion Monte Carlo provides an effective and efficient approach for calculating ground state properties of molecular systems based on potential energy surfaces. The approach has been shown to require increasingly large ensembles when intra- and intermolecular vibrations are weakly coupled. We recently proposed a guided variant of diffusion Monte Carlo to address these challenges for water clusters [Lee, V. G. M.; McCoy, A. B.J. Phys. Chem. A2019, 123, 8063−8070]. In the present study, we extend this approach and apply it to more strongly bound molecular ions, specifically CH5+and H+(H2O)n=1–4. For the protonated water systems, we show that the guided DMC approach that was developed for studies of (H2O)ncan be used to describe the OH stretches and HOH bends in the solvating water molecules, as well as the free OH stretches in the hydronium core. For the hydrogen bonded OH stretches in the H3O+core of H+(H2O)nand the CH stretches in CH5+, we develop adaptive guiding functions based on the instantaneous structure of the ion of interest. Using these guiding functions, we demonstrate that we are able to obtain converged zero-point energies and ground state wave functions using ensemble sizes that are as small as 10% the size that is needed to obtain similar accuracy from unguided calculations.