An efficient and stable hybrid extended Lagrangian/self-consistent field scheme for solving classical mutual induction
An efficient and stable hybrid extended Lagrangian/self-consistent field scheme for solving classical mutual induction
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DOI：
10.1063/1.4933375
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发表时间：
2015-11-07
影响因子：
4.4
通讯作者：
Head-Gordon, Teresa
中科院分区：
文献类型：
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作者：
Albaugh, Alex;Demerdash, Omar;Head-Gordon, Teresa
我们采用了一种混合扩展拉格朗日自一致场（EL/SCF）方法，该方法是为量子电子自由度的时间可逆Born Oppenheimer分子动力学而开发的，用于经典极化问题。在这种情况下，相互感应计算的初始猜测是通过时间可逆速度Verlet格式演化的辅助感应偶极子变量来处理的。然而，我们发现数值不稳定，表现为辅助速度变量的积累，这反过来导致SCF循环次数的增加，以满足在AMOEBA14水模型的1ns轨迹过程中实际诱导偶极子的松散收敛容差。通过将数值不稳定性诊断为破坏动力学的共振问题，我们引入了一个简单的恒温方案，使用Berendsen弱耦合和Nose-Hoover链恒温器说明，应用于辅助偶极子速度。我们发现惯性EL/SCF （iEL/SCF）方法具有较好的能量守恒性，收敛阈值较低，SCF循环次数较少，可以准确地再现NVT和NVE系综中极化模型的所有特性。我们的iEL/SCF方法是对经典互感应计算的标准SCF方法的明显改进，值得研究应用于从头算分子动力学。(C) 2015 AIP出版有限责任公司
We have adapted a hybrid extended Lagrangian self-consistent field (EL/SCF) approach, developed for time reversible Born Oppenheimer molecular dynamics for quantum electronic degrees of freedom, to the problem of classical polarization. In this context, the initial guess for the mutual induction calculation is treated by auxiliary induced dipole variables evolved via a time-reversible velocity Verlet scheme. However, we find numerical instability, which is manifested as an accumulation in the auxiliary velocity variables, that in turn results in an unacceptable increase in the number of SCF cycles to meet even loose convergence tolerances for the real induced dipoles over the course of a 1 ns trajectory of the AMOEBA14 water model. By diagnosing the numerical instability as a problem of resonances that corrupt the dynamics, we introduce a simple thermostating scheme, illustrated using Berendsen weak coupling and Nose-Hoover chain thermostats, applied to the auxiliary dipole velocities. We find that the inertial EL/SCF (iEL/SCF) method provides superior energy conservation with less stringent convergence thresholds and a correspondingly small number of SCF cycles, to reproduce all properties of the polarization model in the NVT and NVE ensembles accurately. Our iEL/SCF approach is a clear improvement over standard SCF approaches to classical mutual induction calculations and would be worth investigating for application to ab initio molecular dynamics as well. (C) 2015 AIP Publishing LLC.