A first-principles study of helium diffusion in quartz and coesite under high pressure up to 12GPa  

作　　者：Hong Liu Lingling Wang Shuchen Li Yaochun Yang Hua Tian Fengxia Sun Chaowen Xu Lei Liu Yi Li Yueju Cui Ying Li Jijun Zhao 

机构地区：[1]United Laboratory of High-Pressure Physics and Earthquake Science,Key Laboratory of Earthquake Prediction,Institute of Earthquake Forecasting,CEA,Beijing 100036,China [2]Key Laboratory of Materials Modification by Laser,Ion and Electron Beams(Dalian University of Technology),Ministry of Education,Dalian 116024,China [3]College of Information Engineering and Computer Science(Tai Yuan University of Technology),Taiyuan 030024,China

出　　处：《Geoscience Frontiers》2021年第2期1001-1009,共9页地学前缘（英文版）

基　　金：the National Natural Science Foundation of China(Grant Nos.41174071,41573121);the open Foundation of the United Laboratory of High-Pressure Physics and Earthquake Science(Grant Nos.2019HPPES06 and 2019HPPES07);the Special Found of the Institute of Earthquake Forecasting,China Earthquake Administration(2018IEF010204);Key Laboratory of Earthquake Prediction,Institute pf Earthquake Forecasting,China Earthquake Administration(2017KLEP03).

摘　　要：Helium diffusion in mantle minerals is crucial for understanding mantle structure and the dynamic processes of Earth's degassing.In this paper,we report helium incorporation and the mechanism of its diffusion in perfect crystals of quartz and coesite.The diffusion pathways,activation energies(Ea),and frequency factors of helium under ambient and high pressure conditions were calculated using Density Functional Theory(DFT)and the climbing image nudged elastic band(CI-NEB)method.The calculated diffusive coefficients of He in the quartz in different orientations are:D[100]=1.24×10^(−6)exp.(−26.83 kJ/mol/RT)m^(2)/s D[010]=1.11×10^(−6)exp.(−31.60 kJ/mol/RT)m^(2)/s.and in the coesite:D[100]=3.00×10^(−7)exp.(−33.79 kJ/mol/RT)m^(2)/s D[001]=2.21×10^(−6)exp.(−18.33 kJ/mol/RT)m^(2)/s.The calculated results indicate that diffusivity of helium is anisotropic in both quartz and coesite and that the degree of anisotropy is much more pronounced in coesite.Helium diffusion behavior in coesite under high pressures was investigated.The activation energies increased with pressure:Ea[100]increased from 33.79 kJ/mol to 58.36 kJ/mol,and Ea[001]increased from 18.33 kJ/mol to 48.87 kJ/mol as pressure increased from0 GPa to 12 GPa.Our calculations showed that helium is not be quantitatively retained in silica at typical surface temperatures on Earth,which is consistent with the findings from previous studies.These results have implications for discussion of the Earth's mantle evolution and for recognition thermal histories of ultra-high pressure(UHP)metamorphic terranes.

关 键 词：HELIUM DIFFUSION QUARTZ COESITE High pressure 

分 类 号：P542[天文地球—构造地质学]