Electronic and optical properties of Be, Ca, Ba and Eu adsorbed on beta-Si3N4 (200) surface based on first-principles calculations

In this work, we have calculated the geometric structure, as well as the electronic and optical properties of Be, Ca, Ba, and Eu adsorption systems by first-principles calculations based on density functional theory. First, the adsorption energy was calculated to verify the stability of the optimized adsorption systems. In addition, the PBE and PBE-TS functions are used for comparison the calculations of Be and Ca adsorption systems. Secondly, the band gap variation of the adsorption system was analyzed by the density of states, and the charge transfer and the properties of chemical bonding properties were investigated by the charge density difference and the Mul-liken population. Finally, the optical properties of the adsorbed beta-Si3N4 (2 0 0) surface were investigated in terms of the dielectric function, absorption spectrum, and reflection spectrum. The lower adsorption energies indicate the superior structural stability of these adsorption systems and the negative adsorption energy of the Eu adsorption system is characteristic of chemisorption. It also exhibits semi-metallic properties and enhances the absorption of visible light. The static dielectric function of these systems decreased after adsorption. The peaks of the absorption and reflection spectra are red-shifted.