s-III型低密度甲烷气体水合物物性的理论研究

Theoretical study on physical properties of s-III low density methane hydrate

摘要:

本文利用基于密度泛函理论的第一性原理赝势平面波方法研究了s-III型水分子笼状结构和s-III型CH4气体水合物笼状结构的晶格常数、体弹模量等基本物性参数，发现在0~2.6 GPa压强范围内两种笼状结构均可以稳定存在，晶胞体积随着压强增大而近似线性减小. s-III型CH4气体水合物中由于CH4分子间的作用力导致甲烷水合物体积发生膨胀，但是体积增大幅度较小且比较均匀，平均增幅在3.97%左右. 最后根据能带结构和电子态密度计算结果发现s-III型CH4气体水合物为绝缘体，不具有导电性.

Abstract:

In this paper, based on the first-principles method the physical parameters such as lattice constants and bulk moduli of water molecules clathrate and methane hydrate with s-III type are studied. Both the two cage structures can be stable in the pressure range of 0-2.6GPa, and the volume decreases approximately linearly with the increasing pressure. The volume of methane hydrate with the s-III type expands due to the interactions between CH4 molecules, but the increase of volume is smaller and uniform with an average increase magnitude of about 3.97%. Finally, it is found that the methane hydrate with s-III type is an insulator and not conductive according to the calculated band structure and electronic density of states of methane hydrate with s-III type.