Phonon dispersions, band structures, and dielectric functions of BeO and BeS polymorphs. (July 2018)

• Record Type: Journal Article
• Authors: Wang, Ke-Long; Gao, Shang-Peng
• Is Part Of: Journal of physics and chemistry of solids. Volume 118(2018)
• Page Start: 242
• Page End: 247
• Publication Date: 2018-07
• Subjects: BeO -- BeS -- DFT -- Phonon dispersion -- GW method -- Bethe-Salpeter equation; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2018.03.013
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Structures, phonon dispersions, electronic structures, and dielectric functions of beryllium oxide (BeO) and beryllium sulfide (BeS) polymorphs are investigated by density functional theory and many-body perturbation theory. Phonon calculations indicate that both wurtzite (w-) and zincblende (zb-) structures are dynamically stable for BeO and BeS, whereas rocksalt (rs-) structures for both BeO and BeS have imaginary phonon frequencies and thus are dynamically unstable at zero pressure. Band structures for the 4 dynamically stable phases show that only w-BeO has a direct band gap. Both the one-shot G0 W0 and quasiparticle self-consistent GW methods are used to correct band energies at high symmetry k -points. Bethe-Salpeter equation (BSE), which considers Coulomb correlated electron–hole pairs, is employed to deal with the computation of macroscopic dielectric functions. It is shown that BSE calculation, employing scissors operator derived by self-consistent GW method, can give dielectric functions agreeing very well with experimental measurement of w-BeO. Weak anisotropic characters can be observed for w-BeO and w-BeS. Both zb-BeS and w-BeS show high optical transition probabilities within a narrow ultraviolet energy range. Highlights: Phonon dispersions show that rocksalt BeO and BeS are dynamically unstable. Zincblende BeO and wurtzite BeS are metastable phases. Excited state properties of BeO and BeS polymorphs are studied by GW method and BSE. QPscGW band gaps of zb-BeO and w-BeS are 9.92 eV and 6.03 eV respectively. Dielectric functions are calculated including electron-hole interaction.