To assess the stability of different reconstructed terminations of the rutile TiO2(110) surface, we apply an ab initio thermodynamics method . In a manner akin to the previously discussed grand canonical free energy, the surfaces are assumed to be in thermodynamic equilibrium with an oxygen-containing gas phase, allowing for the calculation of the surface free energy, 𝛾 surf (110),𝜈 𝑠 :