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Adiabatic Trajectory Approximation within the Framework of Mixed Quantum/Classical Theory
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-11-16 , DOI: 10.1021/acs.jpca.0c07547 Bikramaditya Mandal 1 , Alexander Semenov 1 , Dmitri Babikov 1
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-11-16 , DOI: 10.1021/acs.jpca.0c07547 Bikramaditya Mandal 1 , Alexander Semenov 1 , Dmitri Babikov 1
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A hierarchy of approximate methods is proposed for solving the equations of motion within a framework of the mixed quantum/classical theory (MQCT) of inelastic molecular collisions. Of particular interest is a limiting case: the method in which the classical-like equations of motion for the translational degrees of freedom (scattering) are decoupled from the quantum-like equations for time evolution of the internal molecular states (rotational and vibrational). In practice, trajectories are pre-computed during the first step of calculations with driving forces determined solely by the potential energy surface of the entrance channel, which is an adiabatic trajectory approximation. Quantum state-to-state transition probabilities are computed in the second step of calculations with an expanded basis and very efficient step-size adjustment. Application of this method to H2O + H2 rotationally inelastic scattering shows a significant computational speedup by 2 orders of magnitude. The results of this approximate propagation scheme are still rather accurate, as demonstrated by benchmarking against more rigorous calculations in which the quantum and classical equations of motion are held coupled and against the full-quantum coupled-channel calculations from the literature. It is concluded that the AT-MQCT method (the adiabatic trajectory version of MQCT) represents a promising tool for the computational treatment of molecular collisions and energy exchange.
中文翻译：
混合量子/经典理论框架内的绝热轨迹逼近
提出了一种近似方法的层次结构，用于在非弹性分子碰撞的混合量子/经典理论（MQCT）的框架内求解运动方程。特别令人关注的是一种极限情况：一种方法，其中平移自由度（散射）的经典运动方程与用于内部分子状态（旋转和振动）的时间演化的类量子方程解耦。在实践中，在计算的第一步中使用仅由入口通道的势能面确定的驱动力来预先计算轨迹，这是绝热轨迹近似值。在扩展的基础和非常有效的步长调整基础上的第二步计算中，将计算量子状态到状态的跃迁概率。2 O + H 2旋转非弹性散射显示出显着的计算速度提高了2个数量级。这种近似传播方案的结果仍然相当准确，这是通过对更严格的计算（其中运动和量子方程保持耦合）和文献中的全量子耦合通道计算进行基准测试证明的。结论是，AT-MQCT方法（MQCT的绝热轨迹版本）代表了一种用于分子碰撞和能量交换的计算处理的有前途的工具。
更新日期：2020-11-25
中文翻译：
混合量子/经典理论框架内的绝热轨迹逼近
提出了一种近似方法的层次结构，用于在非弹性分子碰撞的混合量子/经典理论（MQCT）的框架内求解运动方程。特别令人关注的是一种极限情况：一种方法，其中平移自由度（散射）的经典运动方程与用于内部分子状态（旋转和振动）的时间演化的类量子方程解耦。在实践中，在计算的第一步中使用仅由入口通道的势能面确定的驱动力来预先计算轨迹，这是绝热轨迹近似值。在扩展的基础和非常有效的步长调整基础上的第二步计算中，将计算量子状态到状态的跃迁概率。2 O + H 2旋转非弹性散射显示出显着的计算速度提高了2个数量级。这种近似传播方案的结果仍然相当准确，这是通过对更严格的计算（其中运动和量子方程保持耦合）和文献中的全量子耦合通道计算进行基准测试证明的。结论是，AT-MQCT方法（MQCT的绝热轨迹版本）代表了一种用于分子碰撞和能量交换的计算处理的有前途的工具。
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