Mutually polarizable QM/MM model with in situ optimized localized basis functions
Mutually polarizable QM/MM model with in situ optimized localized basis functions
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DOI：
10.1063/1.5080384
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发表时间：
2019-02-21
影响因子：
4.4
通讯作者：
Skylaris, Chris-Kriton
中科院分区：
文献类型：
--
作者：
Dziedzic, Jacek;Head-Gordon, Teresa;Skylaris, Chris-Kriton
我们扩展了我们最近开发的量子力学/分子力学（QM/MM）方法[Dziedzic等人，145，124106（2016）]，以使得能够原位优化定域轨道。量子子系统用ONETEP线性标度密度泛函理论描述，经典子系统用AMOEBA极化力场描述。这两个子系统通过多极静电相互作用，并完全相互极化。对耦合QM/MM系统的哈密顿量采用了总能量最小化方法。我们证明，相比于使用固定基组的简单模型，原位优化基函数提供的额外灵活性提高了QM/MM接口的准确性，但也带来了新的挑战，使QM子系统更容易过极化和非物理电荷转移，由于增加的电荷渗透。我们展示了如何有效地解决这些问题，通过替换经典的排斥性货车的德瓦耳斯项QM/MM相互作用与一个固定的，排斥性MM潜在的，模仿泡利排斥，连同适度增加的QM/MM极化阻尼的电子密度的相互作用。我们验证我们的方法，特别注意氢键，在测试中对水离子对，水二聚体，第一溶剂化壳的中性和带电物种，溶质-溶剂相互作用能。作为原则的证明，我们确定合适的排斥势参数的水，K+，和Cl-。我们所采用的机制，以抵消非物理过极化的QM子系统被证明是足够的，我们的方法是强大的。我们发现，列入明确的偏振在MM的QM/MM部分提高了与完全QM计算的一致性。我们的模型允许使用最小尺寸的QM区域，值得注意的是，在平衡良好的QM/MM界面产生良好的能量。由AIP Publishing授权出版。
We extend our recently developed quantum-mechanical/molecular mechanics (QM/MM) approach [Dziedzic et al., J. Chem. Phys. 145, 124106 ( 2016)] to enable in situ optimization of the localized orbitals. The quantum subsystem is described with ONETEP linear-scaling density functional theory and the classical subsystem - with the AMOEBA polarizable force field. The two subsystems interact via multipolar electrostatics and are fully mutually polarizable. A total energy minimization scheme is employed for the Hamiltonian of the coupled QM/MM system. We demonstrate that, compared to simpler models using fixed basis sets, the additional flexibility offered by in situ optimized basis functions improves the accuracy of the QM/MM interface, but also poses new challenges, making the QM subsystem more prone to overpolarization and unphysical charge transfer due to increased charge penetration. We show how these issues can be efficiently solved by replacing the classical repulsive van der Waals term for QM/MM interactions with an interaction of the electronic density with a fixed, repulsive MM potential that mimics Pauli repulsion, together with a modest increase in the damping of QM/MM polarization. We validate our method, with particular attention paid to the hydrogen bond, in tests on water-ion pairs, the water dimer, first solvation shells of neutral and charged species, and solute-solvent interaction energies. As a proof of principle, we determine suitable repulsive potential parameters for water, K+, and Cl-. The mechanisms we employed to counteract the unphysical overpolarization of the QM subsystem are demonstrated to be adequate, and our approach is robust. We find that the inclusion of explicit polarization in the MM part of QM/MM improves agreement with fully QM calculations. Our model permits the use of minimal size QM regions and, remarkably, yields good energetics across the well-balanced QM/MM interface. Published under license by AIP Publishing.