Esch Michael P, Levine Benjamin G
Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
J Chem Phys. 2020 Sep 21;153(11):114104. doi: 10.1063/5.0022529.
Decoherence corrections increase the accuracy of mixed quantum-classical nonadiabatic molecular dynamics methods, but they typically require explicit knowledge of the potential energy surfaces of all occupied electronic states. This requirement renders them impractical for applications in which large numbers of electronic states are occupied. The authors recently introduced the collapse to a block (TAB) decoherence correction [M. P. Esch and B. G. Levine, J. Chem. Phys. 152, 234105 (2020)], which incorporates a state-pairwise definition of decoherence time to accurately describe dynamics on more than two electronic states. In this work, TAB is extended by introduction of a scheme for efficiently computing a small number of approximate eigenstates of the electronic Hamiltonian, eliminating the need for explicit knowledge of a large number of potential energy surfaces. This adaptation of TAB for dense manifolds of states (TAB-DMS) is systematically improvable by increasing the number of computed approximate eigenstates. Application to a series of one-dimensional model problems demonstrates that TAB-DMS can be accurate when even a very modest number of approximate eigenstates are computed (four in all models tested here). Comparison of TAB simulations to exact quantum dynamical simulations indicates that TAB is quite accurate so long as the decoherence correction is carefully parameterized.
退相干校正提高了混合量子 - 经典非绝热分子动力学方法的准确性，但它们通常需要明确知道所有占据电子态的势能面。这一要求使得它们在大量电子态被占据的应用中不切实际。作者最近引入了塌缩到块（TAB）退相干校正[M. P. 埃施和B. G. 莱文，《化学物理杂志》152, 234105 (2020)]，它采用了成对态的退相干时间定义来准确描述两个以上电子态上的动力学。在这项工作中，通过引入一种有效计算电子哈密顿量少量近似本征态的方案对TAB进行了扩展，从而无需明确知道大量的势能面。这种适用于密集态流形的TAB（TAB - DMS）可以通过增加计算的近似本征态数量来系统地改进。应用于一系列一维模型问题表明，即使计算的近似本征态数量非常少（此处测试的所有模型中均为四个），TAB - DMS也可以是准确的。将TAB模拟与精确量子动力学模拟进行比较表明，只要仔细对退相干校正进行参数化，TAB就相当准确。
