“…43 Thin film Cu 3 VS 4 prepared by pulsed laser deposition (PLD) is also reported to be black with a band gap of 1.35 eV determined by spectroscopic ellipsometry. 44 Two previous density functional theory (DFT) studies performed with the PBE functional 45 reported fundamental indirect band gaps for Cu 3 VS 4 , Cu 3 NbS 4 , and Cu 3 TaS 4 of 1.02 eV, 1.64 eV, and 1.91 eV, respectively, 46 and 1.041 eV, 1.667 eV, and 1.815 eV, respectively, 47 although underestimation of band gap magnitude is a well documented issue with PBE calculations. 48,49 An investigation with Bader analysis predicted effective charges of 0.5, 1.5, and À0.75 on the Cu, transition metal, and S ions, respectively.…”