P. A. Shchepanskyi

Crystals of β-LiNH4SO4 doped with 2 and 5 wt% of Cu2+ and Mn2+ were synthesized. The crystal structure was determined using X-ray diffraction, and the dispersion of refractive indices and birefringence was investigated. The study revealed that adding impurities increased the absolute values of the refractive indices for all crystal physical directions. As the concentration of Mn2+ and Cu2+ impurities increased to 5%, the average refractive index showed an almost linear increase, attributed to the increase in crystal density due to a decrease in the volume of the unit cell. Furthermore, the impurities of Mn2+ and Cu2+ ions significantly altered the absolute values of birefringence. The refractions, electronic polarizabilities, and dispersion parameters were calculated using the Sellmeier formula, showing that adding impurities increased the values of molar refractions and electronic polarizabilities. The study also found that introducing Mn2+ and Cu2+ impurities shifted the optical isotropic point to the long-wavelength part of the spectrum by approximately 26 and 31 nm, respectively.

We report the results of an ab initio study of the linear and ring structures of cadmium telluride clusters [CdTe]_n (Cd_nTe_n) n ≤ 10 within the generalized gradient approximation (GGA) and Purdue–Burke–Ernzerhof (PBE) parameterization with Hubbard corrections (GGA+U). We optimized the linear and ring isomers for each size to obtain the lowest-energy structures and to understand their growth behavior. The cases of n < 8 for ring-type structures and n = 6 and 9 for linear-type structures were found to be the most favorable. All observed clusters with a linear structure were found to have a small highest-occupied–lowest-unoccupied molecular orbital (HOMO–LUMO) gap. The CdTe clusters with ring structure showed larger values of the HOMO–LUMO gaps than the band gap value for the bulk crystal. Structural and electronic properties like bond length, the HOMO–LUMO gap, binding energy, and electronegativity were analyzed.