Ab initio calculations of the electronic structure and specific optical features of β-LiNH4SO4 single crystals

• Published in: Physica. B, Condensed matter Condensed matter, 2018-01, Vol.528, p.37-46
• Main Authors: Rudysh, M.Ya, Brik, M.G., Stadnyk, V.Yo, Brezvin, R.S., Shchepanskyi, P.A., Fedorchuk, A., Khyzhun, O.Y., Kityk, I.V., Piasecki, M.
• Format: Article
• Language: English
• Subjects: Density functional theory (DFT); Electronic band structure; Oxide materials; Refractive index; X-ray spectroscopy
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2017.10.085

In the present work complex experimental and theoretical studies of electronic and optical properties for β-lithium-ammonium sulfate crystals of good optical quality are performed using the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). Standard immersion and spectroscopic techniques accompanied by the theoretical quantum-chemical calculations in the density functional theory (DFT) framework were applied. Calculations of band structure and related properties were carried out within a framework of local density and generalized gradient approximations as well as hybrid B3LYP functionals. The energy levels features and their origin are established from the DFT calculations and they were ferified by XPS and XES measurements. Theoretical and experimental refractive indices dispersions along the principal crystallographic directions (nx, ny and nz) as well as birefringence dispersion (Δnx, Δny and Δnz) in the visible spectral range are obtained. It was found a closeness of nx and ny curves for the titled crystals. More precise birefringence examining predicts their intersection at λ ≈ 190 nm. •Complex experimental and theoretical studies of electronic and optical properties for β-LiNH4SO4 crystals.•X-ray photoelectron spectroscopy and X-ray emission spectroscopy measurements.•Quantum-chemical calculations in the density functional theory (DFT) framework.•Refractive indices dispersions along the principal crystallographic directions as well as birefringence dispersion in the visible spectral range are presented.