Investigations of mechanical and thermoelectric properties of ‘AlNiP’ novel half-Heusler alloy

Abstract

Emergent passion for half-Heusler alloys is due to their drastic thermoelectric properties for tremendous applications in spintronics. The detailed physical insight of the elastic, mechanical, and thermodynamical properties of novel half-Heusler alloy ‘AlNiP’ has been investigated under the framework of Density Functional Theory (DFT). The semi-classical Boltzmann transport theory in combination with DFT is implemented to evaluate the thermoelectric properties. The theoretical computation study related to elastic, mechanical, and thermoelectric properties has been made for the first time. The computed elastic constant values satisfy well the Born-Huang stability criteria, which reveal the mechanical stability of the alloy at the ambient conditions of temperature and pressure. The computed value of Poisson's ratio uncovers the metallic bonding of AlNiP. Furthermore, the elastic properties have been evoked in three dimensions (3D) for Young's modulus, linear compressibility, shear modulus, and Poisson's ratio. Thermodynamic calculations showed that vibrational energy, entropy, and specific heat capacity increases remarkably as temperature increases while vibrational free energy decreases steadily with the increase in temperature. Estimates of Seebeck coefficient (~-12 μV/K at 800 K), lattice thermal conductivity (0.06 W/mK at 300 K), and figure of merit (0.03 at 800 K) have also been put forward in this report. The suitable doping substituent or nano-structuring processes can be an alternative to increase the Seebeck coefficient while keeping the other parameters unperturbed. The studied computational appraisal will certainly stimulate further experimental research of novel half-Heusler alloy AlNiP in pioneering applications.