Elastic, electronic, bonding, and optical properties of WTe2 Weyl semimetal: A comparative investigation with MoTe2 from first principles

Abstract

Td-WTe2 is a topological Weyl semimetal. WTe2 in the orthorhombic structure is stable at room temperature. Elastic, electronic, bonding, and optoelectronic properties of WTe2 have been investigated in detail in this work using the density functional theory. Elastic behaviour together with anisotropy indices of WTe2 have been investigated for the first time. Bonding nature among the constituent atoms and electric field polarization dependent optical constants have also been explored for the first time. WTe2 is elastically anisotropic; optical anisotropy on the other hand is low. The electronic band structure reveals quasi-linear dispersions along certain direction in the Brillouin zone with semi-metallic features. The Fermi level is located at a pseudogap separating bonding and anti-bonding density of states. The electronic effective mass tensor is predicted to be highly direction dependent. The energy dispersion is significantly weaker in the c-direction. The bonding in WTe2 is an admixture of covalent and metallic bonds. Optoelectronic properties show strongly reflecting character over a wide band of photon energies. The compound is a strong absorber of ultraviolet radiation. The Debye temperature has been calculated from the elastic constants. We have compared all the calculated physical properties of WTe2 with those of isostructural MoTe2 Weyl semimetals. The properties of WTe2 and MoTe2 have been compared and contrasted. The calculated parameters of WTe2 have also been compared with those already available in the literature. Very good agreements have been found.