Optical properties

Calculation of the band structure and optical properties of guanidinium aluminum sulfate hexahydrate crystals

B. V. Andrievskii^a, N. A. Romanyuk^b, N. N. Romanyuk^c, O. Ya. Myshchyshyn^d, M. Jaskólski^a, V. I. Stadnik<sup>b

a</sup> Koszalin University of Technology, Koszalin, 75-453, Poland
^b Ivan Franko National University of L'viv
^c Lviv Polytechnic National University
^d Lviv State Academy of Finance, Lviv, 79000, Ukraine

Abstract: The genetic origin of a ferroelectric crystal of guanidinium aluminum sulfate hexahydrate has been established and the spectral dependences of the electron density of states, the electron energy, and the optical functions $\varepsilon_1(\hbar\omega)$ and $\varepsilon_2(\hbar\omega)$ for this crystal have been calculated in terms of the density functional theory. It has been found that there is a weak dependence of the energy of electrons in the upper valence bands on the wave vector. The calculated values of the band gap ($E_g\sim$ 5.44 eV) and refractive indices are in agreement with the experimental results. It has been shown that there is a strong anisotropy of the spectral band $\varepsilon_2(\hbar\omega)$ in the region of 6 eV, which is predominantly formed by the p states of carbon ($\sim$60%) and nitrogen ($\sim$40%) atoms of the C(NH$_2$)$_3$ group.

Received: 22.12.2011
Accepted: 20.01.2012

 English version: Physics of the Solid State, 2012, 54:10, 2066–2072

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