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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Molecular dynamics study of anisotropic translational and rotational diffusion in liquid benzene
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Molecular dynamics study of anisotropic translational and rotational diffusion in liquid benzene

机译：液态苯各向异性平移和旋转扩散的分子动力学研究

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Equilibrium NPT and NVT molecular dynamics simulations were performed on liquid benzene over an extended range of temperature (from 260 to 360 K) using the COMPASS force field. Densities and enthalpies of vaporization (from cohesive energy densities) were within 1% of experiment at all temperatures. tumbling and spinning rotational diffusion coefficients, D-perpendicular to and D-parallel to, computed as a function of temperature, agreed qualitatively with the results of earlier reported experimental and computational investigations. Generally, it was found that D-parallel to/D-perpendicular to approximate to 1.4-2.5 and the activation energy for tumbling was significantly greater than for spinning about the C-6 axis [E-a(D-perpendicular to) = 8.1 kJ mol(-1) and E-a(D-parallel to) = 4.5 kJ mol(-1)]. Calculated translational diffusion coefficients were found to be in quantitative agreement with experimental values at all temperatures [deviations were less than the scatter between different reported measurements]. In addition, translational diffusion coefficients were computed in the molecule-fixed frame to yield values for D-xy (diffusion in the plane of the molecule) and D-z (diffusion perpendicular to the plane). It was found that the ratio D-xy/D-z 2.0, and that the two coefficients have roughly equal activation energies. This represents the first atomistic molecular dynamics study of translational diffusion in the molecular frame.
机译：使用COMPASS力场，在扩展温度范围（260至360 K）上对液态苯进行了NPT和NVT平衡分子动力学模拟。在所有温度下，蒸发的密度和焓（来自内聚能密度）均在实验的1％以内。旋转和旋转旋转扩散系数，D垂直于D平行于D，与温度成函数关系，与先前报道的实验和计算研究的结果定性一致。通常，发现平行于/垂直于D的D大约为1.4-2.5，并且翻滚的活化能明显大于绕C-6轴旋转的活化能[Ea（D垂直于）= 8.1 kJ mol （-1）和Ea（D平行于）= 4.5 kJ mol（-1）]。发现在所有温度下，计算的平移扩散系数与实验值在数量上一致[偏差小于报告的不同测量值之间的差异]。另外，在分子固定的框架内计算平移扩散系数，以得出D-xy（在分子平面内的扩散）和D-z（垂直于平面的扩散）的值。发现比率D-xy / D-z 2.0，并且两个系数具有大致相等的活化能。这代表了分子框架内平移扩散的首次原子分子动力学研究。

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