Abstract
Unlike the conventional zinc-blende II-VI and III-V common-cation systems, which exhibit a general trend of decreasing band gap with increasing anion atomic number, the zinc-blende I-VII cuprous halides CuX (X = Cl, Br, and I) all have an approximately equal direct band gap. Here, using first-principles calculations, we demonstrate that this band gap anomaly in Cu halides is attributed to the unique energy level order of Cu 3d well above X p, making the valence band maximum (VBM) an antibonding state derived mostly from the Cu 3d orbital, thus, a relatively small variation of the band gap with respect to the anion atomic number.
NSTL
Elsevier