Semiconducting and optical properties of selected binary compounds by linear response DFT plus U and hybrid functional methods

This contribution focuses on bulk band gap and dielectric response calculations for copper phosphide Cu3P, using hybrid functionals and linear response DFT+U methods, considering both plane wave and Gaussian-type orbitals basis sets. The semiconducting state of Cu3P is reproduced in good quantitative agreement with experiments when using these methods, at variance with the description provided by standard DFT calculations based on GGA functionals, predicting Cu3P to be a semimetal. Additional DFT+U calculations were performed on zinc blende cadmium selenide CdSe, to further investigate the effect of U on semiconducting binary compounds. For both Cu3P and CdSe, the materials' band gap depends strongly on the on-site repulsion of the nonmetal unfilled p-orbitals, while hybrid functionals still perform well. This suggests that the use of the Hubbard term in DFT+U calculations should be carefully checked for all elements when dealing with semiconducting binary compounds.