Theoretical Study of the Impact of Vacancies and Disorder on the Electronic Properties of Cu_2–xSe

Abstract

Copper selenide (Cu 2−x Se) is a promising material for plasmonic nanoparticle applications. Cu 2−x Se becomes plasmonically active in the oxidized state (x > 0), where free carrier density increases with increasing oxidation. It also has considerable cation (Cu) disorder. To date, there has not been a theoretical study of the impact of the degree of oxidation and cation disorder on the electronic and optical properties of Cu 2−x Se. We used density functional theory (DFT) to investigate the effects of the concentration of Cu vacancies and disorder on the properties of Cu 2−x Se. We used both generalized gradient approximation (GGA) and hybrid-GGA functionals to compute the structural, electronic, and optical properties of the cubic phase of Cu 2−x Se for x = 0, 0.25, 0.5, and 0.75. We performed ab initio molecular dynamics simulations at 300 K to simulate disorder, taking snapshots sampled from simulations of periodic supercells with different levels and arrangements of defects. The HSE06+U hybrid-GGA functional was used to calculate the electronic properties, including the optical band gaps, for a total of 400 different configurations. We found that the average optical band gap increases with increasing oxidation. We also found that only the stoichiometric, x = 0, materials are semiconductors, and the electronic band gap generally increases, increasing disorder.

Computational discovery of diverse functionalities in two-dimensional square disulfide monolayers: auxetic behavior, high curie temperature ferromagnets, electrocatalysts, and photocatalysts

“…[2][3][4][5][6] One particularly exciting area of research involves the investigation of 2D transition metal compounds (TMCs) due to their diverse and intriguing physical properties, including electrical, mechanical, and optical characteristics. [7][8][9][10][11] Notably, certain TMCs have demonstrated potential as electrocatalysts for the hydrogen evolution reaction and as photocatalysts for water splitting, making them promising candidates for clean energy solutions and environmental purication processes. [12][13][14][15] The pursuit of materials with auxetic properties, characterized by a negative Poisson's ratio (NPR) and counterintuitive behavior, has been an active area of research.…”