具有空间变化摩擦的耗散系统中的量子速率
Quantum rates in dissipative systems with spatially varying friction
AI总结：
本研究通过MCTDH、RPMD和RPI方法，探究空间依赖摩擦对耗散反应量子速率的影响，发现量子与经典速率在空间扩散机制中表现定性不同，且RPMD能捕获大部分量子效应。
摘要：
我们研究了使摩擦在反应坐标上空间依赖是否会在耗散反应的热反应速率中引入量子效应。使用数值精确的多组态时间依赖哈特里（MCTDH）方法以及近似的环聚合物分子动力学（RPMD）、环聚合物瞬子（RPI）方法和经典力学计算量子速率。通过在广泛的温度和摩擦强度范围内进行模拟，我们可以识别控制反应动力学的各种机制。在高温下，除了Kramer速率理论预测的空间扩散和能量扩散机制外，在低摩擦下还识别出（相干的）隧穿主导机制。在低温下，非相干隧穿主导Kramer曲线的大部分区域，除非在非常低的摩擦下相干隧穿变得主导。与经典力学不同，浴的影响改变了系统的平衡时间无关性质，导致空间依赖摩擦与核量子效应之间即使在高温下也存在复杂的相互作用。更具体地说，一个现实的摩擦轮廓可以导致在空间扩散机制内量子（经典）速率随摩擦增加（减少），表明经典和量子速率表现出定性不同的行为。除了在非常低的摩擦下，我们发现RPMD捕获了热反应速率中的大部分量子效应。
英文摘要：
We investigate whether making the friction spatially dependent on the reaction coordinate introduces quantum effects into the thermal reaction rates for dissipative reactions. Quantum rates are calculated using the numerically exact multi-configuration time-dependent Hartree (MCTDH) method, as well as the approximate ring-polymer molecular dynamics (RPMD), ring-polymer instanton (RPI) methods, and classical mechanics. By conducting simulations across a wide range of temperatures and friction strengths, we can identify the various regimes that govern the reactive dynamics. At high temperatures, in addition to the spatial-diffusion and energy-diffusion regimes predicted by Kramer's rate theory, a (coherent) tunnelling-dominated regime is identified at low friction. At low temperatures, incoherent tunnelling dominates most of Kramer's curve, except at very low friction when coherent tunnelling becomes dominant. Unlike in classical mechanics, the bath's influence changes the equilibrium time-independent properties of the system, leading to a complex interplay between spatially dependent friction and nuclear quantum effects even at high temperatures. More specifically, a realistic friction profile can lead to an increase (decrease) of the quantum (classical) rates with friction within the spatial-diffusion regime, showing that classical and quantum rates display qualitatively different behaviours. Except at very low frictions, we find that RPMD captures most of the quantum effects in the thermal reaction rates.
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