Electronic structure study of vanadium spinels by using density functional theory and dynamical-mean-field theory

School of Engineering, Indian Institute of Technology Mandi - Kamand 175005, Himachal Pradesh, India

^(a) goluthakur2007@gmail.com

Received: 8 February 2017
Accepted: 3 March 2017

Abstract

Theoretically, various physical properties of AV₂O₄ (A = Zn, Cd and Mg) spinels have been extensively studied for last 15 years. Besides this, no systematic comparative study has been done for these compounds, where the material specific parameters are used. Here, we report the comparative electronic behaviour of these spinels by using a combination of density functional theory and dynamical-mean-field theory, where the self-consistent calculated Coulomb interaction U and Hund's coupling J (determined by the Yukawa screening λ) are used. The main features, such as insulating band gaps , degree of itinerancy of V 3d electrons and position of the lower Hubbard band, are observed for these parameters in these spinels. The calculated values of E_g for ZnV₂O₄, CdV₂O₄ and MgV₂O₄ are found to be ∼0.9 eV, ∼0.95 eV and ∼1.15 eV, respectively, where the values of E_g are close to the experiment for ZnV₂O₄ and MgV₂O₄. The position of the lower Hubbard band are observed around ∼ − 1.05 eV, ∼ − 1.25 eV and ∼ − 1.15 eV for ZnV₂O₄, CdV₂O₄ and MgV₂O₄, respectively, which are also in good agreement with the experimental data for ZnV₂O₄. The order of the average impurity hybridization function of the V site are found to be ZnV₂O₄>MgV₂O₄>CdV₂O₄. Hence, the degree of localization of V 3d electrons is largest for CdV₂O₄ and smallest for ZnV₂O₄, which is in accordance with our earlier results. Hence, the present work shows the importance of material-specific parameters to understand the comparative electronic behaviour of these compounds.