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arXiv 1904.08293physics.chem-ph
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非绝热分子动力学的自旋映射方法

Spin-mapping approach for nonadiabatic molecular dynamics

Johan E. Runeson, Jeremy O. Richardson

摘要:

提出了一种基于量子力学的方法来模拟具有两个耦合电子态的分子系统的非绝热动力学。采用量子力学精确映射的两个层次的问题,自旋1/2相干态,我们构建了一个经典的相空间的自旋矢量约束到一个球面的半径一致的量子幅度的自旋。与Meyer-Miller-Stock-Thoss(MMST)映射中使用的单激发谐振子基不同,该理论不需要在物理态空间中引入额外的投影算子。当处理下的准经典近似,我们表明,由此产生的动力学是等效的MMST哈密顿所产生的。不同的是零点能量参数的值以及初始分布和测量算子。对于各种自旋玻色子模型,我们的方法的结果被认为是一个显着的改进相比,标准Escherichfest动力学和线性化的半经典MMST映射,而不增加任何计算复杂性。

英文摘要:

We propose a trajectory-based method for simulating nonadiabatic dynamics in molecular systems with two coupled electronic states. Employing a quantum-mechanically exact mapping of the two-level problem to a spin-1/2 coherent state, we construct a classical phase space of a spin vector constrained to a spherical surface with a radius consistent with the quantum magnitude of the spin. In contrast with the singly-excited harmonic oscillator basis used in Meyer-Miller-Stock-Thoss (MMST) mapping, the theory requires no additional projection operators onto the space of physical states. When treated under a quasiclassical approximation, we show that the resulting dynamics is equivalent to that generated by the MMST Hamiltonian. What differs is the value of the zero-point energy parameter as well as the initial distribution and the measurement operators. For various spin-boson models the results of our method are seen to be a significant improvement compared to both standard Ehrenfest dynamics and linearized semiclassical MMST mapping, without adding any computational complexity.

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