Modeling Molecular Crystals by QM/MM: Self-Consistent Electrostatic Embedding for Geometry Optimizations and Molecular Property Calculations in the Solid
Modeling Molecular Crystals by QM/MM: Self-Consistent Electrostatic Embedding for Geometry Optimizations and Molecular Property Calculations in the Solid
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DOI：
10.1021/ct200824r
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发表时间：
2012-02-01
影响因子：
5.5
通讯作者：
Buehl, Michael
中科院分区：
文献类型：
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作者：
Bjornsson, Ragnar;Buehl, Michael
我们提出了一种使用自适应量子力学/分子力学（QM/MM）为基础的协议的分子晶体模型的方法。在适当的QM水平下描述感兴趣的分子（或其较大的簇），并将其嵌入由晶体结构信息构建的MM原子的大阵列中。非键MM力场由原子为中心的点电荷和Lennard-Jones势组成，使用UFF力场的货车范德华参数。点电荷最初来自于单分子DFT计算，然后在点电荷领域自洽地更新。额外的电荷安装在MM簇周围，以校正丢失的长程静电效应。中心络合物的几何形状可以通过周围MM反应场中的量子化学计算来放松，从而捕获几何形状上的固态效应。我们通过成功模拟HCN-BF 3的巨大气-固键收缩、再现固体VOCl 3的B-DFT质量局部几何结构的能力以及[Ru（eta（5）-Cp *）（eta（3）-CH2CHCHC6H5）（NCCH 3）（2）]（2+）（一种固态的困难钌烯丙基络合物）的几何结构，证明了这种方法用于几何结构优化的准确性。我们进一步表明，该协议是非常适合于随后的分子性质的计算在固态（准确的放松的几何形状往往是必需的），例如过渡金属NMR和EFG计算VOCl 3和钒儿茶酚复合物在固态。
We present an approach to model molecular crystals using an adaptive quantum mechanics/molecular mechanics (QM/MM) based protocol. The molecule of interest (or a larger cluster thereof) is described at an appropriate QM level and is embedded in a large array of MM atoms built up from crystal structure information. The nonbonded MM force field consists of atom-centered point charges and Lennard-Jones potentials using van der Waals parameters from the UFF force field. The point charges are initially derived from a single molecule DFT calculation and are then updated self-consistently in the field of point charges. Additional charges are fitted around the MM cluster to correct for missing long-range electrostatic effects. The geometry of the central complex can then be relaxed by quantum chemical calculations in the surrounding MM reaction field, hence capturing solid-state effects on the geometry. We demonstrate the accuracy of this approach for geometry optimization by successful modeling of the huge gas-to-solid bond contraction of HCN-BF3, the ability to reproduce periodic-DFT quality local geometries of solid VOCl3, and the geometry of [Ru(eta(5)-Cp*)(eta(3)-CH2CHCHC6H5)(NCCH3)(2)](2+), a difficult ruthenium allyl complex in the solid state. We further show that this protocol is well suited for subsequent molecular property calculations in the solid state (where accurate relaxed geometries are often required) as exemplified by transition metal NMR and EFG calculations of VOCl3 and a vanadium catechol complex in the solid state.