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

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) m2 /sD[010] = 1.11 × 10−6 exp. (−31.60 kJ / mol / RT) m2 /s