Proper Thermal Equilibration of Simulations with Drude Polarizable Models: Temperature-Grouped Dual-Nosé–Hoover Thermostat
Proper Thermal Equilibration of Simulations with Drude Polarizable Models: Temperature-Grouped Dual-Nosé–Hoover Thermostat
复制标题
使用 Drude 极化模型进行模拟的正确热平衡：温度分组双 Nosé–Hoover 恒温器
DOI：
10.1021/acs.jpclett.9b02983
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Yethiraj, Arun
中科院分区：
文献类型：
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作者：
Son, Chang Yun;McDaniel, Jesse G.;Cui, Qiang;Yethiraj, Arun
电子极化的显式处理对于准确模拟高电荷态或界面体系至关重要。与迭代自洽场(SCF)方法相比，扩展拉格朗日方法对于使用可极化力场的模拟具有更高的计算效率。然而，必须选择适当的恒温器，以最大限度地减少热流，并确保所有不受约束的系统自由度之间的动能均匀分配。本文以水、氯化钠/水、丙酮和离子液体(IL)BMIM+/BF4-为例，研究了不同的恒温器对具有Drude极化力场的凝聚相体系模拟的影响。我们发现，传统的双温度恒温器方案经常受到等分和绝热电子态的破坏，导致静态和动态性质都有相当大的误差。从实际自由度到Drude自由度的热流导致稳定的温度梯度，并使系统处于错误的有效温度。具有高频内部自由度的系统，如平面不适当的二面体或C-H键伸展，是最脆弱的；这个问题在文献中被很大程度上忽视了，因为主要关注刚性水分子的模拟。我们提出了一种新的温度分组双头́-Hoover恒温器，其中分子质心平移被分配给与其余自由度分开的温度群。我们证明，无论恒温器的耦合强度如何，该方案都能正确地预测所有测试系统的静态和动态特性。这种新的恒温器已经在GPU加速的OpenMM模拟包中实现，并且相对于SCF方案保持了显著的加速比。
An explicit treatment of electronic polarization is critically important to accurate simulations of highly charged or interfacial systems. Compared to the iterative self-consistent field (SCF) scheme, extended Lagrangian approaches are computationally more efficient for simulations that employ a polarizable force field. However, an appropriate thermostat must be chosen to minimize heat flow and ensure an equipartition of kinetic energy among all unconstrained system degrees of freedom. Here we investigate the effects of different thermostats on the simulation of condensed phase systems with the Drude polarizable force field using several examples that include water, NaCl/water, acetone, and an ionic liquid (IL) BMIM+/BF4–. We show that conventional dual-temperature thermostat schemes often suffer from violations of equipartitioning and adiabatic electronic state, leading to considerable errors in both static and dynamic properties. Heat flow from the real degrees of freedom to the Drude degrees of freedom leads to a steady temperature gradient and puts the system at an incorrect effective temperature. Systems with high-frequency internal degrees of freedom such as planar improper dihedrals or C–H bond stretches are most vulnerable; this issue has been largely overlooked in the literature because of the primary focus on simulations of rigid water molecules. We present a new temperature-grouped dual-Nosé–Hoover thermostat, where the molecular center of mass translations are assigned to a temperature group separated from the rest degrees of freedom. We demonstrate that this scheme predicts correct static and dynamic properties for all the systems tested here, regardless of the thermostat coupling strength. This new thermostat has been implemented into the GPU-accelerated OpenMM simulation package and maintains a significant speedup relative to the SCF scheme.