Accurate Molecular Crystal Lattice Energies from a Fragment QM/MM Approach with On-the-Fly Ab Initio Force Field Parametrization

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• 作者：Shuhao Wen ; Gregory J. O. Beran
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2011
• 出版时间：November 8, 2011
• 年：2011
• 卷：7
• 期：11
• 页码：3733-3742
• 全文大小：947K
• 年卷期：v.7,no.11(November 8, 2011)
• ISSN：1549-9626

文摘

We combine quantum and classical mechanics in a fragment-based many-body interaction model to predict organic molecular crystal lattice energies. Individual molecules in the central unit cell and their short-range pairwise interactions are modeled quantum mechanically, while long-range pairwise and many-body interactions are approximated classically. The classical contributions are evaluated using an accurate ab initio force field that is constructed on-the-fly from quantum mechanical calculations on the individual molecules in the unit cell. The force field parameters include ab initio distributed multipole moments, distributed polarizabilities, and isotropic two- and three-body atomic dispersion coefficients. This QM/MM fragment model reproduces full periodic MP2 lattice energies to within a couple kJ/mol at substantially reduced cost. When high-level electronic structure methods are coupled with the ab initio force field, molecular crystal lattice energies are predicted to within 2 kJ/mol of their experimental values for six of the seven crystals examined here. Finally, Axilrod鈥揟eller鈥揗uto three-body dispersion energy plays a nontrivial role in several of the molecular crystals studied here.