Lattice vibrations and the energy landscape of the isoelectronic semiconductor series CuBr, ZnSe, GaAs, and Ge: The special case of CuBr and its d-level chemistry
Joseph Woicik, Eric J. Cockayne, Eric L. Shirley, Igor Levin, Conan Weiland, Bruce D. Ravel, A. M. Milinda Abeykoon
We have examined the lattice vibrations and the energy landscape of the isoelectronic diamond and zincblende semiconductor series CuBr, ZnSe, GaAs, and Ge. Vibrations are found to be an increasing function of ionicity, with the cation sublattice always vibrating with larger amplitude than the anion sublattice. These findings are consistent with density-functional-theory calculations of the energy landscape and temperature-dependent molecular-dynamics simulations of the local atomic fluctuations. For the case of CuBr, strong vibrations produce unprecedented changes in the near-edge x-ray absorption fine structure that we have successfully modelled utilizing only ground-state electronic-structure calculations plus solution of the Bethe-Salpeter equation to treat excited-state core-hole interactions with no additional input other than the mean-squared relative displacements or Debye-Waller factors of the ions obtained from the molecular-dynamics simulations. Structural refinements in CuBr using large atomic configurations to simultaneously fit x-ray absorption and x-ray total-scattering data support these conclusions, and they reveal strong Cu-Br first-neighbor correlations and asymmetric distributions of interatomic distances in the temperature ranges of both negative and positive thermal expansion. The inclusion of the Cu 3d Hubbard-U term in density-functional theory is found necessary to stabilize CuBr in the zincblende structure and to bring its vibrational amplitudes into agreement with experiment. Delineation of the CuBr photoemission valence-band spectrum demonstrates the chemical hybridization between Cu 3d and Br 4p states in qualitative agreement with the density-functional theory results.
, Cockayne, E.
, Shirley, E.
, Levin, I.
, Weiland, C.
, Ravel, B.
and Abeykoon, A.
Lattice vibrations and the energy landscape of the isoelectronic semiconductor series CuBr, ZnSe, GaAs, and Ge: The special case of CuBr and its d-level chemistry, Physical Review B, [online], https://doi.org/10.1103/PhysRevB.108.195202, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956137
(Accessed February 21, 2024)