First-Principles Calculations of Structural, Elastic, Electronic, and Optical Properties of Pure and Tm2+-Doped Alkali‒Earth Chlorides MCl2 (M = Ca, Sr, and Ba)

Abstract

The structural, elastic, and electronic properties of pure and Tm2+-doped alkali–earth chlorides are studied in detail using the hybrid density-functional theory as implemented in the CRYSTAL09 code. The calculated local geometrical structures of the dopant site, Mulliken populations, electronic-band structures, and density of states for the pure and doped crystals are analyzed and compared to reveal the changes induced by the impurity ion. Additionally, the electronic and optical properties of the Tm2+-ions doped into alkali–earth chlorides are modeled by employing the exchange-charge model of the semi-empirical crystal-field theory with the help of the optimized local coordination structures around impurities. The successful simulation of the 4f-5d transition spectrum of Tm2+ ions in SrCl2 is demonstrated as an example to show the validity of the combined theoretical scheme of the first-principles and crystal-field models.