Low-Index Stoichiometric Surfaces Of Cubiw2o8

CuBiW2O8 (CBTO), a theoretically predicted, recently synthesized novel quaternary metal oxide, has been identified as a promising solar light absorber. In the present paper, the surface properties of CBTO are studied to further examine the applicability of the material for solar energy applications. Surface studies of quaternary oxides via first principles methods are rare in the literature. We present here a systematic approach to identifying stable surfaces and the origin of their stability. First, the emergence of the electronic properties from the interplay of cations is explored in bulk CBTO. Calculated XRD data is used to label the surfaces on the experimental XRD plot. For the dominant low-index stoichiometric surfaces, we calculate surface bond strengths, cleaving energies, and surface energies via the slab model within periodic boundary conditions. To calculate the surface energies of a quaternary oxide such as CBTO, we review the existing methodologies and propose a guideline for defining the lower and upper bounds of the slab thickness used in the linear fit model. Surface energies are then used to predict the equilibrium crystal shape via Wulff construction.