Zhang Meimei, Lussetti Enrico, de Souza Luís E S, Müller-Plathe Florian
International University Bremen, P.O. Box 750 561, D-28725 Bremen, Germany.
J Phys Chem B. 2005 Aug 11;109(31):15060-7. doi: 10.1021/jp0512255.
The reverse nonequilibrium molecular dynamics method for thermal conductivities is adapted to the investigation of molecular fluids. The method generates a heat flux through the system by suitably exchanging velocities of particles located in different regions. From the resulting temperature gradient, the thermal conductivity is then calculated. Different variants of the algorithm and their combinations with other system parameters are tested: exchange of atomic velocities versus exchange of molecular center-of-mass velocities, different exchange frequencies, molecular models with bond constraints versus models with flexible bonds, united-atom versus all-atom models, and presence versus absence of a thermostat. To help establish the range of applicability, the algorithm is tested on different models of benzene, cyclohexane, water, and n-hexane. We find that the algorithm is robust and that the calculated thermal conductivities are insensitive to variations in its control parameters. The force field, in contrast, has a major influence on the value of the thermal conductivity. While calculated and experimental thermal conductivities fall into the same order of magnitude, in most cases the calculated values are systematically larger. United-atom force fields seem to do better than all-atom force fields, possibly because they remove high-frequency degrees of freedom from the simulation, which, in nature, are quantum-mechanical oscillators in their ground state and do not contribute to heat conduction.
用于热导率的反向非平衡分子动力学方法被应用于分子流体的研究。该方法通过适当地交换位于不同区域的粒子的速度，在系统中产生热通量。然后根据产生的温度梯度计算热导率。测试了该算法的不同变体及其与其他系统参数的组合：原子速度交换与分子质心速度交换、不同的交换频率、具有键约束的分子模型与具有柔性键的模型、联合原子模型与全原子模型，以及是否存在恒温器。为了帮助确定适用范围，该算法在苯、环己烷、水和正己烷的不同模型上进行了测试。我们发现该算法是稳健的，并且计算得到的热导率对其控制参数的变化不敏感。相比之下，力场对热导率的值有重大影响。虽然计算得到的热导率和实验热导率处于同一数量级，但在大多数情况下，计算值系统性地更大。联合原子力场似乎比全原子力场表现更好，可能是因为它们从模拟中去除了高频自由度，而这些自由度在本质上是处于基态的量子力学振荡器，对热传导没有贡献。
