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Path integral simulation study of quantum dynamics of hydrogen doped inside carbon nanotubes

碳纳米管内掺氢量子动力学的路径积分模拟研究

基本信息

批准号：
18550018
负责人：
KINUGAWA Kenichi
金额：
$ 2.63万
依托单位：
Nara Women's University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18550018/
关键词：
nanotube-fullerene new energy hydrogen simulation technology

项目摘要

The centroid path integral molecular dynamics (CMD) simulations have been carried out for the systems of para-hydrogen contained inside the carbon nanotubes. For these simulations the CMD source program for numerical calculations has newly been developed. We have employed the isothermal-isobaric ensemble molecular dynamics technique to keep the pressure tensor along the z-direction constant and the temperature arising from all the degrees of freedom constant as well. The Andersen-type isobaric technique and the Nose-Hoover chain-type isothermal technique have been employed for this purpose. As for molecular interaction, the Silvera-Goldman potential and the Lennard-Jones potential have been assumed to be valid for the hydrogen-hydrogen and the hydrogen-carbon interaction, respectively. For the latter interaction, the nanotube inner wall has been smoothed out over the whole spatial range so that the nanotube wall should have flat and uniform surface without identification of carbon atoms. The CMD simulations for this model have been performed at the condition that the number of hydrogen molecules is 312, the temperature is 8-15 K, and Trotter number is 100. The anisotropy of dynamics has been clarified on the basis of the analysis of the mean square displacement and the velocity autocorrelation function of imaginary time path integral centroids of hydrogen molecules. Furthermore, it has been found that the hydrogen inside the nanotube tends to have higher melting temperature than the bulk system. As a reference of the nanotube hydrogen system, the physical properties of bulk hydrogen revealed by means of the CMD simulations have been reviewed as well.

采用质心路径积分分子动力学（CMD）方法对碳纳米管中的仲氢体系进行了模拟。对于这些模拟的CMD源程序的数值计算已经新开发。我们采用等温等压系综分子动力学技术来保持压力张量沿着z方向恒定和温度所产生的所有自由度以及常数。Andersen型等压技术和Nose-Hoover链型等温技术已用于此目的。对于分子间相互作用，我们分别假设Silvera-Goldman势和Lennard-Jones势适用于氢-氢相互作用和氢-碳相互作用。对于后一种相互作用，纳米管内壁在整个空间范围内被平滑，使得纳米管壁应该具有平坦和均匀的表面，而不需要识别碳原子。在氢分子数为312、温度为8-15 K、Trotter数为100的条件下对该模型进行了CMD模拟。通过对氢分子虚时程积分质心的均方位移和速度自相关函数的分析，阐明了氢分子动力学的各向异性。此外，已经发现纳米管内部的氢倾向于具有比本体系统更高的熔化温度。作为纳米管氢系统的参考，体相氢的物理性质揭示的CMD模拟方法进行了审查以及。