Restructuring of the Pt3Sn(111) surfaces induced by atomicand molecular oxygen from first principles

摘要

The surface restructuring of Pt_3Sn(111) induced by oxygen chemisorption is examined by means ofdensity-functional theory calculations. Molecular and atomic oxygen chemisorption is investigated on the two available terminations of the bulk alloy—(2 X 2) and (3(2/1~X 3(2/1~)R30°—these two surfacesdiffering by the tin content and the nature of chemical sites. An extensive geometric, energetic, andvibrational analysis is performed including the influence of oxygen coverage in the case of atomicadsorption. For molecular adsorption, regular structures have been obtained for both surfaces witha clear effect of tin on the stability of the adsorption forms. In contrast, for atomic adsorption, twooxygen chemical states are found. In particular, a peculiar surface restructuring, involving theformation of a network of SnO_2 species, appears for large oxygen coverage. However the twoterminations present discrepancies for the restructuring mechanism all along the oxygen coverageincrease. All these results are supported by a systematic vibrational ana