arXiv 1901.043962019-01-14physics.comp-phphysics.chem-ph

量子蒙特卡罗中力常数矩阵的直接计算

Direct evaluation of the force constant matrix in quantum Monte Carlo

Yu Yang Fredrik Liu, Bartholomew Andrews, Gareth J. Conduit

发表信息：: J. Chem. Phys., 150(3):034104, Jan 2019
DOI：: 10.1063/1.5070138

摘要：

我们开发了一种形式主义，直接评估矩阵的力常数内的量子蒙特卡罗计算。我们利用矩阵的力常数，以准确地放松的原子在分子中的位置，并确定其振动模式，使用变分和扩散蒙特卡罗相结合。计算的键长与实验结果的差异小于0.007 π。对于氢气和氯化氢，我们获得的基本振动频率在实验结果的0.1%以内，比领先的计算方法精确约10倍。对于二氧化碳和甲烷，所获得的振动频率平均在实验结果的1.1%以内，这比使用具有Perdew-Burke-Ernzerhof（PBE）泛函的受限Hartree-Fock和密度泛函理论的结果至少接近3倍，并且比具有半经验泛函的密度泛函理论相当或更好。

英文摘要：

We develop a formalism to directly evaluate the matrix of force constants within a Quantum Monte Carlo calculation. We utilize the matrix of force constants to accurately relax the positions of atoms in molecules and determine their vibrational modes, using a combination of Variational and Diffusion Monte Carlo. The computed bond lengths differ by less than 0.007Å from the experimental results for all four tested molecules. For hydrogen and hydrogen chloride, we obtain fundamental vibrational frequencies within 0.1% of experimental results and ~10 times more accurate than leading computational methods. For carbon dioxide and methane, the vibrational frequency obtained is on average within 1.1% of the experimental result, which is at least 3 times closer than results using Restricted Hartree-Fock and Density Functional Theory with a Perdew-Burke-Ernzerhof (PBE) functional and comparable or better than Density Functional Theory with a semi-empirical functional.

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