Investigation on prospective thermoelectrics — cubic Nd-doped LMO and rhombohedral Cu4Mn2Te4 materials — first principles approach

Abstract

Structural, electronic, magnetic and optical properties of Cu4Mn2Te4 have been reported earlier by the authors, and here, the transport properties of the same are discussed along with the band structure investigation of the neodymium-doped cubic material LMO (LiMn2O4), namely LiMn[Formula: see text]Nd[Formula: see text]O4 compound, under spin polarized schemes through the First Principles calculations. The Full Potential-Linearized Augumented Plane Wave Method (FP-LAPW) method is adopted to investigate the electronic structures based on the framework of Density Functional Theory (DFT). Exchange potentials are treated using the Generalized Gradient Approximations (GGA). Cohesive energy calculations reveal that the ferromagnetic phase of LiMn[Formula: see text]Nd[Formula: see text]O4 and the antiferromagnetic phase of Cu4Mn2Te4 exhibits a stable phase. Of these, FM-LiMn[Formula: see text]Nd[Formula: see text]O4 shows a semi-metallic-like behavior in spin-up channel and metallic behavior in spin-down channel whereas antiferromagnetic Cu4Mn2Te4 exhibits a band gap in both spin-up and spin-down channels. Dirac points are identified at −0.0625[Formula: see text]eV in the band structure plot of FM-LiMn[Formula: see text]Nd[Formula: see text]O4 at its high symmetry points [Formula: see text] and W which is an indication of high electron mobility at ambient condition. The presence of flat and dispersive bands around the Fermi energy level is an indication of high thermopower, and it is present in both the compounds FM-LiMn[Formula: see text]Nd[Formula: see text]O4 and AFM-Cu4Mn2Te4. From the present computations, at 300[Formula: see text]K, a power factor range of ([Formula: see text] scaled by relaxation time in [Formula: see text]W/msK2) [Formula: see text] and [Formula: see text] is obtained for ferromagnetic LiMn[Formula: see text]Nd[Formula: see text]O4 compounds at up and down spins, respectively. A typical power factor ([Formula: see text]Wm[Formula: see text]s[Formula: see text]K[Formula: see text]) of [Formula: see text] and [Formula: see text] is obtained for antiferromagnetic Cu4Mn2Te4 at 325[Formula: see text]K required for good thermoelectric performance.