DFT insights into new B-containing 212 MAX phases: Hf2AB2 (A = In, Sn)

TL;DR

This study uses first-principles calculations to explore the mechanical, thermal, and optical properties of new Hf2AB2 MAX phases with boride components, revealing their enhanced properties and potential applications.

Contribution

It provides the first detailed theoretical analysis of the properties of Hf2AB2 (A=In, Sn) MAX phases, demonstrating their stability and superior properties compared to similar compounds.

Findings

Hf2AB2 compounds are mechanically stable and thermodynamically favorable.

Hf2SnB2 exhibits higher hardness and strength than Hf2InB2.

Thermal and optical properties of Hf2AB2 are superior to related MAX phases.

Abstract

212 MAX phase borides are new additions to the MAX phase family with enhanced thermo-mechanical properties. In this article, first-principles calculations have been carried out to explore the mechanical properties, Vickers hardness, elastic anisotropy, thermal properties, and optical properties of predicted thermodynamically stable MAX compounds Hf2AB2 (A = In, Sn). The structural properties are compared with the available data to assess the validity of calculations. The mechanical stability of Hf2AB2 (A = In, Sn) compounds is established with the help of the computed stiffness constants (Cij). The possible reason for enhanced mechanical properties and Vickers hardness of Hf2SnB2 is explained based on the analysis of bonding strength, followed by the electronic density of states. Higher mechanical strength and Vickers hardness of Hf2AB2 (A = In, Sn) compared to Hf2AC (A = In, Sn) are also indicated in the light of charge density mapping. The values of Pugh ratio, Poissons ratio and Cauchy pressure predict brittle character of the studied compounds. Besides, the anisotropic nature of the titled borides is investigated by 2D and 3D plots of elastic moduli along with some well established anisotropy indices. Thermal properties were investigated by calculating the Debye temperature, minimum thermal conductivity, Gr\"uneisen parameter, and melting temperature. The thermal properties of Hf2AB2 (A = In, Sn) are also superior to Hf2AC (A = In, Sn). The optical constants such as real and imaginary parts of the dielectric function, refractive index, extinction coefficient, absorption coefficient, photoconductivity, reflectivity, and loss function are investigated.