An ab-initio study on structural, elastic, electronic, bonding, thermal, and optical properties of topological Weyl semimetal TaX (X = P, As)

Abstract

In recent days, study of topological Weyl semimetals have become an active branch of physics and materials science because they led to realization of the Weyl fermions and exhibited protected Fermi arc surface states. Therefore, topological Weyl semimetals TaX (X = P, As) are important electronic systems to investigate both from the point of view of fundamental physics and potential applications. In this work, we have studied the structural, elastic, mechanical, electronic, bonding, acoustic, thermal and optical properties of TaX (X = P, As) in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that both TaP and TaAs possesses low to medium level of elastic anisotropy (depending on the measure), reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature and melting temperature. The minimum thermal conductivities and anisotropies of TaX (X = P, As) are calculated. Bond population analysis supports the bonding nature as predicted by the elastic parameters. The bulk electronic band structure calculations reveal clear semi-metallic features with quasi-linear energy dispersions in certain sections of the Brillouin zone near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding states indicates significant electronic stability of tetragonal TaX (X = P, As).The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes TaX suitable as reflecting coating. TaX (X = P, As) are very efficient absorber of ultraviolet radiation. Both the compounds are moderately optically anisotropic owing to the anisotropic nature of the electronic band structure. The refractive indices are very high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations.

A comprehensive DFT based insights into the physical properties of tetragonal superconducting Mo5PB2

“…Thus, machinability index of a material is an important parameter. It is dominated by number of variables, like the elastic properties or characteristics of the work materials, cutting tool material, tool geometry, the nature of tool engagement with the work, cutting conditions, type of cutting, cutting fluid, and machine tool rigidity, hardness and its capacity [53]. The cutting force, tool wear and many more properties of a material are determined by its machinability index.…”

“…The values of A L range between 0 to 10.26, and for almost 90% of the solids A L greater than 1. Moreover, it has been argued that A L can also indicate the presence of layered/lamellar type of structure in a solid [35,53,69]. Materials with strong layered and non layered structure can be predicted from the higher and lower values of A L , respectively.…”

“…Study of a material having same or different acoustic impedance with the surrounding medium has become a considerable interest in transducer design, noise reduction in aircraft engine, industrial factories, and many underwater acoustic applications [53]. The acoustic impedance is an important parameter which determines the transfer of acoustic energy between two media.…”

“…On the other hand, if the impedances differ greatly, most of it is reflected causing transmitted signal loss and echo generation. The acoustic impedance, Z, of a material is obtained from [53]:…”

First‐Principles Calculations to Investigate the Third‐Order Elastic Constants and Mechanical Properties of Mg, Be, Ti, Zn, Zr, and Cd

“…However, it is very difficult to obtain a complete set of TOECs from experimental methods for HCP metals, so it is eager to predict the TOECs of HCP metals by using theoretical methods. ere are quite a few of the available theoretical methods for determining TOECs, including empirical force-constant models [9][10][11][12][13], molecular-dynamics simulations [14,15], and first-principles total-energy methods [1,16]. Nielson and Martin first applied to the methods of first-principles total-energy calculations determining TOECs of materials [17,18].…”