Sonu Sharma

Investigation of thermoelectric properties of half-metallic Co2MnGe by using first principles calculations

By combining the electronic structures obtained from first principles calculations with Boltzmann transport theory we have investigated the electronic, magnetic and transport properties of the Co2MnGe Heusler compound. The density of state plots, dispersion curves and the total energy of paramagnetic and ferromagnetic (FM) phases clearly show the half-metallic FM ground state for the compound, with an indirect band gap of about 400 meV in the minority spin channel. It has an integer value of the magnetic moment equal to 5 μ(B). In the FM phase a very large value (∼ 550 µV K(-1)) of the Seebeck coefficient (S) is obtained for down-spin electrons due to the existence of an almost flat conduction band along X in the Γ direction. The two-current model has been used to find the total S and the obtained value is about 10 µV K(-1). The calculated values of the Seebeck coefficient, resistivity and electronic thermal conductivity show nice agreement with the experimental results.

Investigation of the electronic and thermoelectric properties of Fe2ScX (X = P, As and Sb) full Heusler alloys by using first principles calculations

By using ab initio electronic structure calculations here we report the three new full Heusler alloys—Fe2ScP, Fe2ScAs and Fe2ScSb. These alloys possess a very good thermoelectric behavior and are also expected to be synthesized in laboratories. The first two compounds are indirect band gap semiconductors and the last one shows a semimetallic ground state. The value of the band gap of Fe2ScP and Fe2ScAs is 0.3 eV and 0.09 eV, respectively. The presence of flat conduction bands along the Γ—X-direction suggest the large electron like effective mass and also promises a very good thermoelectric behavior of these compounds. At 200 K, the Seebeck coefficients of Fe2ScP, Fe2ScAs and Fe2ScSb compounds are −770, −386 and −192 µV K−1, respectively. The maximum power factor (PF) is expected for the n-type doping in these materials. The heavily doped Fe2ScP and Fe2ScAs have PF > 60 for a wide temperature range, which is comparable to the PF of Bi2Te3—a well known and one of the most commercially used thermoelectric materials. The present work suggests the possible thermoelectric applicability of these materials in a wide temperature range.

Applicability of two-current model in understanding the electronic transport behavior of inverse Heusler alloy: Fe2CoSi

Abstract Here we explore the applicability of the two-current model in understanding the transport behavior of Fe2CoSi compound by using the first principles calculations in combination with the Boltzmann transport theory. The spin-up channel has small DOS at the E F , whereas spin-dn channel shows almost zero DOS at the E F . The absolute value of Seebeck coefficient in the spin-up channel shows linear increment with the temperature and in the spin-dn channel it varies non-linearly. The electrical conductivity also shows non-linear temperature dependence in both the spin channels whereas, the electronic thermal conductivity shows linear temperature dependence. The values of transport coefficients and their temperature dependence obtained by using the two-current model are found to be in fairly good agreement with the experimental data. Present work clearly suggests the importance of two-current model in understanding the transport properties of the compound.

Understanding the transport properties of YNiBi half- Heusler alloy: An Ab-initio study

In the present work, we have studied the electronic and transport properties of YNiBi half-Heusler alloy by combining the first principles methods with the Boltzmann transport theory. The electronic band structure and total density of states plot suggest the presence of semiconducting ground state in the compound. The value of indirect band gap is found to be ∼0.21 eV. The origin of the band gap is associated primarily with the interaction between the Ni 3d and the Y 4d states. The room temperature value of Seebeck coefficient is ∼230u2005µVK−1. A moderate power factor of about 12×1014 μ Wcm−1 K−2 s−1 is obtained at 980u2005k.