Theoretical studies of the pressure-induced phase transition and elastic properties of BeS

Sound velocities and Debye temperature of BeSe under high pressure up to 50 GPa

“…From 0 to 50 GPa, the values of the ratio (B/G) of BeSe are inferior to 1.75; which suggest that this compound is prone to brittle behavior. At zero-pressure, our calculated value of B/G of BeSe material is relatively lower from the value 1.37 obtained by Ji et al [2] for BeS compound, indicating a brittle nature of berylliumchalcogenides (BeS and BeSe) at low pressure. The crystal density ρ reported in Table. 2 is also plotted in Figure.1.…”

“…They found that the elastic constants and the Valence band width of all compounds increase monotony with increasing pressure, while the transverse (vt) and average (vm) wave velocities become almost constants with increasing pressure. The effect of high pressure on the phase transition and the variation of some other physical properties of BeS compound under pressure have been investigated by Ji et al [2]. They found that the longitudinal wave velocity (vl) of BeS compound in its cubic zincblende structure increases with pressure, while the transverse (vt) and average (vm) wave velocities become almost constants with increasing pressure.…”

Sound velocities and thermal properties of BeX (X=S, Se and Te) alkaline-earth chalcogenides

“…[6]. For BeS material, Ji et al [11] have investigated the effect of high pressure on the longitudinal (vl), transverse (vt) and average (vm) wave velocities. Despite, Ji et al [11] did not give the exact numerical values (the results are given in curves and not in tables) which allow making an exact comparison; our results are in very good agreement with these of Ji et al [11].…”

“…This important observation is consistent well the present case since the bond-length of BeS (d = 2.107 Å) is smaller than that of BeSe (d= 2.224 Å), which is also smaller than that of BeTe (d= 2.432 Å). The melting temperature of several crystals can be estimated as function of the elastic constant C11 by [11], [17]:…”

“…They found that the phonon dispersion curves of these materials in cubic zincblende phase depict their dynamical stability in this phase at ambient condition. They found also that the variation of lattice-specific heat with temperature of these compounds obeys the classical Dulong-Petit's law at high temperature, while at low-temperature it obeys the Debye's T 3 law Ji et al [11] have investigated the effect of high pressure on the phase's transition and several other properties of BeS material. They found that for both B3 and B8 phases, the longitudinal wave (vl) changes faster than the transverse waves (vt).…”