Role of van der Waals corrections for the PtX2 (X = O, S, Se) compounds

Dispersion (van derWaals) forces play an important role in determining the structural properties of the systems where dispersion is crucial, for example, layerlike crystals (CdI2 type). Thus, to contribute to the understanding of the role of van der Waals (vdW) corrections for the PtX2 (X = O, S, Se) compounds, we report a density functional theory (DFT) investigation within nonlocal vdW corrections for the atomic structure and electronic properties of bulk PtX2. From our calculations, we identified the lowest energy structures, CaCl2 type for PtO2 and CdI2 type for both PtS2 and PtSe2, i.e., CdI2 type is not the lowest energy structure for PtO2. We reported the structural changes for higher energy PtX2 systems and the changes in the stability order compared with plain DFT-PBE calculations. The structural changes induced by vdW corrections affects the electronic structure of the layered CdI2-type structures (PtS2 and PtSe2), where a metallic behavior is obtained in contrast to PBE calculations, which yields an energy separation between the unoccupied and occupied states.