对密度泛函理论和点电荷力场在描述sI甲烷水合物中的性能与扩散蒙特卡罗的比较
Benchmarking the performance of Density Functional Theory and Point Charge Force Fields in their Description of sI Methane Hydrate against Diffusion Monte Carlo
摘要：
高质量的参考数据，从扩散蒙特卡罗计算散装SI甲烷水合物，复杂的晶体表现出氢键和分散为主的相互作用。评价了几种常用的交换关联泛函和全原子点电荷力场的性能。我们的研究结果表明，没有一个测试的交换相关泛函是足够的能量和结构的甲烷水合物准确地描述，而点电荷力场表现不好，在他们的描述的结合能，但公平以及解离能量。通过比较冰Ih，我们表明，一个很好的预测水合物的体积和内聚能主要依赖于一个准确的描述的氢键水框架，但要正确地预测水合物的稳定性相对于解离冰Ih和甲烷气体，准确的水-甲烷相互作用也是必需的。我们的结果突出了密度泛函理论在描述氢键水框架和分散束缚甲烷时所面临的困难。
英文摘要：
High quality reference data from diffusion Monte Carlo calculations are presented for bulk sI methane hydrate, a complex crystal exhibiting both hydrogen-bond and dispersion dominated interactions. The performance of some commonly used exchange-correlation functionals and all-atom point charge force fields is evaluated. Our results show that none of the exchange-correlation functionals tested are sufficient to describe both the energetics and the structure of methane hydrate accurately, whilst the point charge force fields perform badly in their description of the cohesive energy but fair well for the dissociation energetics. By comparing to ice Ih, we show that a good prediction of the volume and cohesive energies for the hydrate relies primarily on an accurate description of the hydrogen bonded water framework, but that to correctly predict stability of the hydrate with respect to dissociation to ice Ih and methane gas, accuracy in the water-methane interaction is also required. Our results highlight the difficulty that density functional theory faces in describing both the hydrogen bonded water framework and the dispersion bound methane.
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