Temperature Dependence of Elastic and Ultrasonic Properties of Sodium Borohydride

Abstract

We present the temperature dependent elastic and ultrasonic properties of sodium borohydride. The second and third order elastic constants of NaBH 4 have been computed in the temperature range 0-300K using Coulomb and Born-Mayer potentials. The sodium borohydride crystallizes into NaCl-type structure. The computed values of second order elastic constants have been applied to evaluate the temperature dependent mechanical properties such as bulk modulus, shear modulus, tetragonal modulus, Poisson's ratio and Zener anisotropy factor and ultrasonic velocity to predict futuristic information about sodium borohydride. The fracture to toughness ratio (bulk modulus/shear modulus) in sodium borohydride varied from 1.91 to 1.62, which shows its behavioral change from ductile to brittle on increasing the temperature. Then, ultrasonic Grüneisen parameters have been computed with the use of elastic constants in the temperature regime 100-300K. The obtained results have been discussed in correlation with available experimental and theoretical results.

Theoretical investigation of acoustic wave velocity of aluminum phosphide under pressure

“…Hence, there are three types of velocities exits, one is the longitudinal wave velocity (Vp) and others two are the shear waves velocities (Vs1, Vs2). These three types of velocities depend on the direction of the propagation of the wave in the crystal [8]. The expressions for direction dependent ultrasonic velocities in cubic crystals can be described as function of the elastic constants Cij and the density ρ as follows [8].…”

“…These three types of velocities depend on the direction of the propagation of the wave in the crystal [8]. The expressions for direction dependent ultrasonic velocities in cubic crystals can be described as function of the elastic constants Cij and the density ρ as follows [8]. The different relationships used here are detailed elsewhere [9].…”

“…Vsw (kms -1 ) = 4.088 -0.329 p + 4.17x10 -2 p 2 -2.07x10 -3 p 3 (8) Vsw (kms -1 ) = 4.335 -0.343 p + 4.45x10 -2 p 2 -2.25x10 -3 p 3 (9) It is important to note that the same behavior of the surface acoustic wave speeds under compression was also observed in cubic zincblende AlN compound [16] for both [100] and [110] directions. To the best of authors' knowledge, there are no data available in the literature on the surface acoustic wave speeds for AlP semiconducting material.…”