Using density functional theory in combination with the ab initio atomistic thermodynamics approach, we studied the structure and stability of Re͑1010͒ surfaces in contact with an oxygen atmosphere. The calculations indicate that without adsorption of oxygen, the surface is unreconstructed, but adsorption of more than 2 geometrical monolayers causes a ͑1 ϫ 3͒ reconstruction, resembling a surface being composed of ͕1011͖ microfacets. This structure is able to rationalize the different experimental observations obtained on Re͑1010͒ and will be of relevance for catalytic reactions under oxygen-rich conditions. In this work, density functional theory is used in conjunction with the ab initio atomistic thermodynamics approach 17-20 to evaluate the ͑p , T͒-dependent surface free energies from first principles.
A. DFT calculationsDFT energies for different oxygen overlayers on the surfaces were evaluated using the CASTEP code 21 with Vanderbilt-type ultrasoft pseudopotentials ͑PPs͒ ͑Ref. 22͒