Optical, half-metallic and thermoelectric properties of the Co 2 TaAl [001] film
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ORIGINAL PAPER
Optical, half-metallic and thermoelectric properties of the Co2TaAl [001] film R Mohebbi, A Boochani*
and S Rezaee
Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran Received: 24 September 2019 / Accepted: 06 March 2020
Abstract: Based on the density functional theory framework and GGA approximation, the structural, electronic, optical and thermoelectric properties of the Co2TaAl and its [001] films have been calculated. The Co2TaAl compound has great hardness with the bulk modulus of 201.5 GPa which is bigger than steel. This compound has half-metallic nature with 100% spin polarization in the Fermi surface and 2.0lB magnetic moment. Due to its the real and imaginary dielectric function responses in the visible region and very low Eloss and extinction, this compound is a suitable case for optical applications in visible area energy. The Co2TaAl, also has a suitable thermoelectric efficiency in all temperatures, for a spin down with big power factor in high temperatures which is suitable for power generation applications. The energy-volume and thermodynamic phase diagrams of the [001] films are indicate, their stability, in the mechanical and thermodynamic views. The electronic diagrams showed the half-metallic behavior of the TaAl termination with 100% spin polarization, by the 0.25 eV energy gap in the down spin. The optical response of the TaAl termination for the E\z direction is similar to that of the bulk case and has a red shift, but in the Ekz the metallic nature is reduced. The merit amount of the TaAl termination is 0.7 in the lower temperatures for a down spin and its Seebeck has been greater than that of the bulk case. Keywords: DFT; Co2TaAl [001] film; Half-metallic properties; Optical properties; Thermoelectric Properties
1. Introduction After discovering the half-metals, many efforts have been made to find the new half-metals, theoretically and experimentally. In this regard, various compounds including Heusler compounds have been discovered [1–4]. Heusler structures have the FCC base and are divided into two groups of full-Heusler and half-Heusler compounds. The full-Heusler compounds with the X2YZ stoichiometric and symbol are crystallized into two space groups of Fm3m F 43m, in which the elements X and Y belong to transition metals and Z is one of the elements in groups III to V of the periodic table. The half-filled d orbitals of the X and Y atoms with their atomic arrangement in the unit cell and the bond types are the main factors to make the ferromagnetic behavior possible. Recently, these compounds have attracted much attention due to their interesting physical behavior, such as half-metallic [5], elastic responses [6], Xray absorption spectra (XAS) [7] and thermoelectric
*Corresponding author, E-mail: [email protected]
behaviors [8]. Cobalt-based compounds are the most famous among these materials, which have attracted attention in recent years due to their strongly ferromagnetic properties, Curie temperature and thermoelectric beh
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