Density functional theory calculations and thermodynamic analysis of the forsterite Mg₂SiO₄(010) surface

The stability of possible termination structures for the (010) surface of forsterite, $ Mg_2SiO_4 $, is studied using a density functional theory (DFT) based thermodynamic approach. The DFT calculations are used to estimate the surface Gibbs free energy of various surface structures and compare their stability as a function of the chemical environment. Among 9 possible terminations, the SiO-II, M2, O-II terminations are found to be most stable as conditions range from Mg-poor to Mg-rich. This relative stability order remains the same at an elevated temperature. The surface phase diagram obtained provides ground for further theoretical studies of chemical processes on forsterite surfaces in terrestrial planets.