  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.
