Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
J Chem Phys. 2012 Feb 21;136(7):074101. doi: 10.1063/1.3681391.
A thorough examination of the use of fixed-node diffusion Monte Carlo for the study of rotation-vibration mixing in systems that undergo large amplitude vibrational motions is reported. Using H(3)(+) as a model system, the overall accuracy of the method is tested by comparing the results of these calculations with those from converged variational calculations. The effects of the presence of a large amplitude inversion mode on rotation-vibration mixing are considered by comparing the H(3)(+) results with those for H(3)O(+). Finally, analysis of the results of the fixed-node diffusion Monte Carlo calculations performed in different nodal regions is found to provide clear indications of when some of the methodology's underlying assumptions are breaking down as well as provide physical insights into the form of the rotation-vibration coupling that is most likely responsible.
本文全面考察了固定节点扩散蒙特卡罗在研究经历大幅振动运动的体系中的转动-振动混合的应用。以 H(3)(+)作为模型体系，通过将这些计算的结果与收敛变分计算的结果进行比较，测试了该方法的整体准确性。通过比较 H(3)(+)和 H(3)O(+)的结果，研究了存在大振幅反转模式对转动-振动混合的影响。最后，对在不同节点区域执行的固定节点扩散蒙特卡罗计算的结果进行分析，发现这些结果能够清晰地表明，在某些情况下，该方法的一些基本假设开始失效，并为最有可能起作用的转动-振动耦合形式提供物理上的理解。
