[en] The pressure-induced phase transformation from B3 to B1 structures in ZnS using first-principle projector-augmented wave method is studied. To understand the nature and driving force behind the transition, the interesting properties in both phases, including enthalpy, phonon dispersion curves and elastic constants, are systematically investigated. The results show that the calculated transition pressure is within the range of 16.33 GPa to 19.04 GPa, which is in good agreement with the available experimental and theoretical data. The transition process can be viewed as the appearance and disappearance of very slight lattice distortion accompanied by the movement of Zn and S atoms along the [111] crystallographic axis. The physical driving force of the B3–B1 phase transition is confirmed to be a coupling effect between the mechanical instability of B3 phase under pressure and the softening acoustic phonon mode resulting from the pressure-induced lattice deformation. For B1 phase, it is further predicted that a new phase transition takes place at about 59.9 GPa. - Highlights: • The phase transformation from B3 to B1 structures in ZnS is studied using first-principle method. • The predicted transition pressure is within the range of 16.33 to 19.04 GPa. • The transition process can be viewed as the appearance and disappearance of very slight lattice distortion. • Physical driving force of the transition is a coupling effect between the mechanical instability and softening phonon. • For B1 phase, it is further predicted that a new phase transition takes place at about 59.9 GPa.

[en] The results of Er³⁺ ion spectroscopic analysis in Sc:LiNbO₃ crystals were reported. The line strengths from the ground state to the excited state were evaluated from the measured unpolarized absorption spectrum and analyzed by using standard Judd-Ofelt theory. For Sc(3 mol. %):Er (1 mol. %):LiNbO₃ crystal, the obtained intensity parameters are: Ω₂=3.72 x 10^-20 cm², Ω₄=1.07 x 10^-20 cm², and Ω₆=0.98 x 10^-20 cm². The fluorescence spectra and microsecond time-resolved spectra were investigated in the visible region. The excited state absorption transition strengths at 800 nm excitation were evaluated based on Judd-Ofelt theory. The results obtained here were compared to results from other research on Er:LiNbO₃ crystals. (orig.)