a priori path integral simulation on the dynamical properties and phenomena of low-temperature quantum molecular systems

本文采用路径积分质心分子动力学（CMD）方法，对固态氢和液态氢的静态和动态性质进行了非经验研究，得到了固态仲氢的声子激发态，其能量高于以往的实验报道.虽然由于实验中相互矛盾的数据，固体仲氢中高能区的声子色散已经被确定，但我们的研究对这一突出的争议有了深入的了解，我们使用CMD模拟评估了基本的输运性质（自扩散系数，热导率，剪切粘度和体粘度）。这项工作是第一次尝试在数值上先验估计任何量子液体的集体输运性质。特别是，自扩散系数和剪切粘度的计算值与实验值的协议是优秀的。另一方面，经典的分子动力学模拟得到的数值与实验值有很大的偏差。这表明液态仲氢输运性质的本质特征来自于量子效应。这一系列研究的显著之处在于，它们解决了任何其他计算技术所不能揭示的动力学性质。

In the present series of studies, the static and dynamical properties of solid and liquid hydrogen have been non-empirically investigated by means of path integral centroid molecular dynamics (CMD) simulations.For solid para-hydrogen, we have obtained the phonon excitations with higher energies than those in previous experimental reports. Although the phonon dispersion in the high energy region in solid para-hydrogen has been definitely determined because of contradictory data reported from the experiments, our present study have thrown an insight into this outstanding controversy.The fundamental transport properties (self-diffusion coefficient, thermal conductivity, shear viscosity, and bulk viscosity) have been evaluated by using the CMD simulations. This work is the first attempt to numerically a priori estimate collective transport properties of any quantum liquids. In particular, the agreement of calculated self-diffusion coefficient and the shear viscosity with experimental values is excellent. On the other hand, the classical molecular dynamics simulations have yield the values much deviated from the experimental ones. This indicates that the essential features of the transport properties of liquid para-hydrogen comes from the quantum effect.The present series of studies are remarkable in that they have resolved the dynamical properties which cannot be revealed by any other computational techniques.