Crystal and electronic structure of the sub-stoichiometric photocatalyst Cu4Se6: DFT study

作者：Kevorkyants, Ruslan^*; Farooq, Saima; Tizaoui, Chedly

来源：Journal of Physics and Chemistry of Solids, 2022, 162: 110529.

DOI：10.1016/j.jpcs.2021.110529

• Photocatalysis
• DFT
• Cu 2-x Se
• Electronic structure
• Molecular modeling

Copper selenides being earth-abundant advanced functional materials have paramount significance due to their substantial absorption characteristics and structural diversity. In this study, the crystal and electronic structure of hypothetical visible-light photocatalyst Cu4Se6 have been systematically investigated by density functional theory (DFT) calculations. Given a primitive unit cell of the parent pristine CuSe (P63/mmc) compound at most five symmetry-unique copper-deficient Cu4Se6 polymorphs can be constructed. DFT calculations with PBE (Perdew-Burke-Ernzerhof) density functional identify two of them (P63/mc and P63/mmc) as potential photocatalysts. It was found that accurate description of their electronic structures requires inclusion of spin-orbit coupling (SOC). Temperature effect on the electronic structures was modeled via uniform crystal lattice expansion/contraction (<5%). The computed PBE + SOC bandgap maxima of 1.57 eV (P63/mc) and 1.41 eV (P63/mmc) correspond to the lattice expansion of 4% and 3%, respectively. Since the P63/mc Cu4Se6 polymorph is lower in energy than its P63/mmc counterpart by 2.56 eV we concluded that the former would be preferentially formed in actual experiment. This work might prove to be instrumental in the design of new photocatalysts from the Cu2-xSe family.

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