Zirconium trigallide polymorphs with tetragonal and cubic structures: optical and thermodynamic properties

An ab initio investigation of optical and thermodynamic properties of two polymorphs of intermetallic compound Ga3Zr has been carried out by the plane-wave pseudopotential method based on density functional theory. Frequency-dependent dielectric matrix is used to determine the imaginary part of the dielectric function from which the real part has been obtained through Kramers–Kronig relations. Other optical properties, namely optical conductivity, absorption coefficient and reflectivity, are also determined. The analysis of all optical functions reveals that tetragonal Ga3Zr is slightly optically anisotropic. The absorption spectra having metallic nature show both of these to be promising materials for absorbing radiation in the UV region. The reflectivity spectra are compared with those of several compounds in the low-energy range. Due to high reflectivity in the IR and visible regions, both the studied polymorphs are promising as good coating materials in order to avoid solar heating and also as radiative cooling materials. Furthermore, the temperature and pressure dependences of all the thermodynamic parameters of the polymorphs with the cubic and tetragonal structures are calculated and analyzed for the first time using the quasi-harmonic Debye model.