Which Is Better at Predicting Quantum-Tunneling Rates: Quantum Transition-State Theory or Free-Energy Instanton Theory?
Which Is Better at Predicting Quantum-Tunneling Rates: Quantum Transition-State Theory or Free-Energy Instanton Theory?
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DOI：
10.1021/jz501889v
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发表时间：
2014-11
期刊：
影响因子：
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通讯作者：
Yanchuan Zhang;T. Stecher;Marko T. Cvitas;S. Althorpe
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作者：
Yanchuan Zhang;T. Stecher;Marko T. Cvitas;S. Althorpe
量子过渡态理论（QTST）和自由能瞬子理论（FEIT）是两种密切相关的方法，用于从反应势垒处的自由能估计量子速率系数。在一维模型的计算中，FEIT通常比QTST更接近协议，在所有温度下的交叉深隧穿的确切量子结果，这表明FEIT是一个更好的近似比QTST在这个政权。在这里，我们表明，这个简单的趋势并不适用于更大维度的系统。我们报告几个共线和三维反应的测试，其中QTST优于FEIT在一系列的温度低于交叉，这可以延伸到一半的交叉温度（低于该FEIT优于QTST）。这表明，QTST为基础的方法，如环聚合物分子动力学（RPMD）往往可以给出更接近的协议，确切的量子结果比FEIT。
Quantum transition-state theory (QTST) and free-energy instanton theory (FEIT) are two closely related methods for estimating the quantum rate coefficient from the free-energy at the reaction barrier. In calculations on one-dimensional models, FEIT typically gives closer agreement than QTST with the exact quantum results at all temperatures below the crossover to deep tunneling, suggesting that FEIT is a better approximation than QTST in this regime. Here we show that this simple trend does not hold for systems of greater dimensionality. We report tests on several collinear and three-dimensional reactions, in which QTST outperforms FEIT over a range of temperatures below crossover, which can extend down to half the crossover temperature (below which FEIT outperforms QTST). This suggests that QTST-based methods such as ring-polymer molecular dynamics (RPMD) may often give closer agreement with the exact quantum results than FEIT.