Energetics and structure of stoichiometric SnO2 surfaces studied by first-principles calculations

First-principles calculations based on density-functional theory, ultrasoft pseudopotentials and plane-wave basis sets are used to investigate the energetics and the relaxed ionic positions of several low-index stoichiometric SnO2 surfaces. We find that, in order of increasing energy, the surfaces form the sequence (110)<(100)<(101)<(001). The prediction that (110) is the most stable surface agrees with earlier experimental and theoretical indications, but the relative stability found for (100) and (101) disagrees with earlier shell-model predictions. Ionic relaxations at all four surfaces are moderate, with no displacement exceeding ca. 0.3 إ. Comparisons with theoretical and experimental results for the ionic relaxations at the same surfaces of TiO2 are presented.