Structural, elastic, electronic, bonding, and optical properties of topological CaSn3 semimetal

Abstract

In recent days, topological semimetals have become an active branch of materials research. The topological Weyl semimetal CaSn 3 , belonging to the AuCu 3 type cubic structure, is an important electronic system to investigate both from the point of view of fundamental physics and prospective applications. In this work, we have studied the structural, elastic, mechanical, electronic, bonding, Fermi surface and optical properties of CaSn 3 in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that CaSn 3 possesses low level of elastic anisotropy, reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature. The mechanical stability conditions are fulfilled. Analysis of bond population supports the bonding nature as indicated by the elastic parameters. The bulk electronic band structure reveals clear semimetallic features with signature Dirac cone-like dispersions near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding peaks points towards significant electronic stability of cubic CaSn 3 . The Fermi surface mostly consists of electron-like sheets with very few small hole pockets. The band structure is fairly isotropic in the k-space. The optical constants show interesting characteristics. The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing infrared to midultraviolet regions. High reflectivity over wide spectral range makes CaSn 3 a suitable material for reflecting coating. CaSn 3 is an efficient absorber of ultraviolet radiation. The refractive index is very high in the infrared to visible range. All the energy dependent optical parameters exhibit clear metallic signatures and are in complete accord with the underlying bulk electronic density of states calculations.Structural, elastic, electronic (with and without SOC), magnetic, enthalpy, vibrational, electron phonon coupling, and some thermal properties have been studied for CaSn 3 [22 -24] so far. Among these, elastic properties have been explored lightly, and to the best of our knowledge, a detailed study of elastic properties including Cauchy pressure, tetragonal shear modulus, Kleinman parameter, machinability index, hardness, and anisotropy in elastic moduli are still lacking. The acoustic velocities, Debye temperature, electronic properties related to the Fermi surface, charge density distribution of atoms, Mulliken bond population analysis and optical properties of CaSn 3 have not yet been discussed theoretically and experimentally at all. As far as possible applications are concerned, a thorough understanding of the elastic and mechanical response of a compound is essential. This enables us to predict the behavior of the material under

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

“…The calculated values of hardness of TaP and TaAs are 18.07GPa and 14.07 GPa, respectively. It is seen from Table 3 that compared to other well-known WSMs [5][6][7] , the elastic moduli of TaX are significantly larger.…”

“…It is important to note that we have not included SOC in our electronic band structure calculations. A number of previous studies on variety of topological WSMs and topological insulators [5][6][7]135 belonging to different crystal classes have demonstrated that, as far as the bulk physical properties described in this work are concerned, inclusion of SOC has only a minimal effect. None of the conclusions drawn from our investigation is affected significantly by the SOC.…”

“…TaP is significantly harder than TaAs but TaAs shows better machinability compared to TaP. It is instructive to note that the machinability indices of TaX (X = P, As) are comparable to widely mentioned MAX phase nanolaminates and other layered ternary and binary compounds including topological systems [5][6][7][125][126][127][128][129][130] . The high hardness of TaP is quite remarkable and exceeds that for many MAX phase compounds and related systems 120,[125][126][127][128][129][130][131][132][133][134] .…”

“…The optical constants spectra of both TaP and TaAs show close agreement with the underlying electronic band structure. The absorption coefficients of TaP and TaAs are very high in the ultraviolet region compared to other topological electronic systems [5][6][7] . The refractive indices of both the compounds are also very high in the infrared-visible region.…”

“…These properties make WSMs interesting for the future applications in electronic, spintronic and quantum computing devices. Besides there exists a large number of technologically important properties of WSMs in different crystal classes which are largely insensitive to the spin–orbit coupling (SOC) which mainly give rise to the exotic features in the surface and bulk electronic band structure 5 – 7 .…”