Molecular Dynamics Study of Self-Diffusion of Silica and Oxygen in Silica Melt
详细信息
- 责任者：Sun Yicheng (School of Earth Sciences and Engineering ; Nanjing University ; Nanjing 210093 ; China) ; Zhou Huiqun
- 刊名：Geological Journal of China Universities
- 出版年：2013
- 卷期：19(3)
- 关键词：二氧化硅 ; silica
- 页码：p.456-462
- 图表：5 illus., 2 tables, 38 refs.
- 分类号：0700
- issnNo：ISSN1006-7493
- isbnNo：CN32-1440/P
摘要
The diffusivity of elements in mineral controls the processes of ion exchange,isotope fractionation,and phase transition.As one of the most important components of silicate melts,SiO2 plays a very important role in the earth mantle structure and the dynamics process.This paper focuses on the ion diffusion mechanism in silica melt and the corresponding pressure when the self-diffusion coefficient reaches its maximum value.We calculated the changing process of Si and O ions,self-diffusion coefficient at temperatures of 3000 K by using the molecular dynamics(MD) simulation which contains 4500 ions in the silica melt with Morse stretch potential.Calculations show that both Si and O self-diffusion coefficients increase at initial compression and reach maximum values at 17.5 GPa.Self-diffusion coefficients for O are slightly greater than that for Si.The Si and O ions,diffusion feature is caused by a defect-controlled transport mechanism and the five-fold coordination structure of Si ion is the main reason for the rise of the diffusion coefficients in accord with the increasing pressure.The fact that the diffusion coefficient reaches its maximum value means the change in the formation of five-fold Si in the liquid silica.This paper also calculated the relationship between the average volume of [SiO2 ] unit and the pressure,which agrees well with the results of our experiment.