Phase transition of CaTe induced by high-pressure: Structural and elastic DFT study of five structures

Anomalous Lattice Thermal Conductivity in Rocksalt IIA–VIA Compounds

“…Because all the studied MX (M = Mg, Ca, Sr, and Ba and X = O, S, Se, and Te) compounds crystallize in the cubic ( Fm 3̅ m ) structure, they have three independent elastic constants such as longitudinal ( C 11 ), transverse ( C 12 ), and shear ( C 44 ) due to symmetry constraints ( C 11 = C 22 = C 33 , C 12 = C 13 = C 23 , C 44 = C 55 = C 66 , and C ij = C ji ). The calculated second-order elastic constants are given in Table S4 and are consistent with the available ultrasonic pulse echo − and Brillouin scattering measurements as well as with previous first-principles calculations. ,,,− The obtained elastic constants satisfy the Born stability criteria indicating the mechanical stability of all these MX (M = Mg, Ca, Sr, and Ba and X = O, S, Se, and Te) compounds. We then computed bulk ( B ) and shear ( G ) moduli from the calculated elastic constants with Voigt–Reuss–Hill (VRH) approximation using eqs and , respectively. Later, the obtained B and G values are used to calculate Young’s modulus ( E ) using eq .…”

Mass density, sound velocity and Debye temperature of CaTe semiconductor under high compression

“…For all these compounds, they found that the elastic constant C11 increases monotonously with enhanced pressure up to 30 GPa, while both the elastic constants C12 and C44 remain almost unchanged with increasing pressure from 0 up to 30 GPa. Using first principles calculations, Labidi et al [6] have studied the structural parameters, elastic constants and the thermodynamic properties of CaS, CaSe, and CaTe compounds in the temperature ranging from 0 to 100 K, while in the same context, Maizi et al [7] have studied the same properties in the pressure ranging from 0 to 30 GPa and temperature ranging from 0 to 1200 K. In the present contribution, we studied the high hydrostatic compression effect up to 27.8 GPa on the variation of the mass density,sound velocity and Debye temperature of CaTe compound using the structural parameters and the elastic constants reported by Guo et al [1].…”

“…where νl and νt are the longitudinal and transverse sound velocity obtained using the shear modulus G, the bulk modulus B and the density g from Navier's equations: v l = [(3B+4G)/3ρ] 1/2 , and vt= (G/ρ) 1/2 [13], [16]. Using the elastic constants Cij(p) and the lattice parameter a (p) calculated by Guo et al [1], the compression effects on the longitudinal νl, transverse νt and average vm sound velocity for CaTe compound are illustrated in Fig. 2.…”

“…It is known that alkaline earth chalcogenides (AECs) just like calcium sulfide (CaS), calcium selenide (CaSe) and calcium telluride (CaTe) semiconductors have great importance in many technological applications including catalysis, microelectronics, etc [1]. Using density functional theory (DFT) calculations, Guo et al [1] have studied the structural phase transition of crystalline CaTe in pressure ranging from 0 to 60 GPa. They found that under high compression the cubic rocksalt (B1) phase of CaTe compound transforms to an intermediate tetragonal structure of P4/nmm at pressure of 27.8 GPa.…”

“…They found that under high compression the cubic rocksalt (B1) phase of CaTe compound transforms to an intermediate tetragonal structure of P4/nmm at pressure of 27.8 GPa. Guo et al [1] have studied also the pressure dependence of mechanical properties of CaTe with five different forms, and the change of the elastic constants. Luo et al [2] have investigated experimentally the structural phase transition of calcium (Ca) based chalcogenides CaX (X = S, Se, Te) compounds up to 52 GPa using energy-dispersive x-ray-diffraction techniques with a synchrotron source.…”