The present paper addresses the temperature dependent elastic, mechanical and thermal properties of NaCl structure (B1 type) holmium monopnictides, HoX (X = N, P, As, Sb, Bi) computed using Coulomb and Born repulsive potentials extended up to second nearest neighbors. The second-order elastic constants (SOECs) of single crystals HoX are calculated as a function of temperature in the range 0–500[Formula: see text]K. The compounds under study are found to be brittle in nature. Beside these calculations, the theoretical hardness has been obtained for various rare-earth monopnictides using the elastic properties in the polycrystalline approach. The obtained hardness values indicate HoN to be hard, but cannot be considered super hard. The anisotropic nature of the chosen single crystal is an important physical quantity in studying the directional dependent thermal properties such as Debye temperature and thermal conductivity computed using ultrasonic velocities along different crystallographic directions. The obtained results are discussed in correlation with mechanical and thermophysical properties of similar materials.

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We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX ( X : N , P , As , Sb and Bi ) along the 〈100〉, 〈110〉, 〈111〉 in the temperature range 100–500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born–Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0–500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon–phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

The anisotropic elastic constants of a B2 structured iron aluminide FeAl (Fe-40 at. % Al) alloy at different temperatures are computed using Coulomb and Born Mayer model. The temperature dependent ultrasonic properties of the alloy along with other associated parameters are determined using the elastic constants. The correlation between the mechanical and thermal properties makes ultrasonic properties a suitable, nondestructive tool to study the physical state of FeAl alloy. The results of present investigation are discussed in correlation with the microstructural phenomenon like phonon-phonon interaction and the other thermophysical properties. Temperature dependence of ultrasonic attenuation along different crystallographic directions reveals some typical characteristic features.

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