Ab initio Investigation of the Structure and Electronic Properties of Normal Spinel Fe2SiO4

Transition metal spinel oxides have recently been predicted to create efficient transparent conducting oxides for optoelectronic devices. These compounds can be easily tuned by doping or defect to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still subject to controversy. We propose a complete density functional theory investigation of fayalite (Fe2SiO4) spinel, using Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA) in order to explain the electronic and structural properties of this material. A detailed study of their crystal structure and electronic structure is given and compared with experimental data. The lattice parameters calculated are in agreement with the lattice obtained experimentally. The band structure of Fe2SiO4 spinel without Coulomb parameter U shows that the bands close to Fermi energy appear to be a band metal, with four iron d-bands crossing the Fermi level, in spite of the fact that from the experiment it is found to be an insulator.

Modulating the optical and magnetic properties of geometrically frustrated ZnV2O4 by the introduction of indium (nonmagnetic ions), iron, and chromium (magnetic ions)

The current study is aimed at understanding the effects of diluting the magnetic properties of a geometrically frustrated normal spinel, ZnV2O4, with the incorporation of nonmagnetic In3+ in place of V3+.

Normal spinel structure ZnFe2O4/g-C3N4 enhanced catalytic activity for photo-Fenton degradation of methylene blue

Heterogeneous photo-Fenton technology has been widely employed to degrade organic dyes in wasterwater. In the present study, a composite consisting of normal spinel structure ZnFe2O4 nanoparticle and two-dimensional sheet of g-C3N4 was facilely synthesized. Different characterization technologies, such as XRD, XPS and VSM, were employed to demonstrate the normal spinel structure ZnFe2O4 formation. The composite shows higher catalytic activity for degradation of methylene blue (MB) than mixed spinel structure ZnFe2O4/g-C3N4. Simultaneously, the composite exhibits excellent stability and reusability.

Understanding the Electronic Transition of Normal Spinel Structure of Co3O4 Using GGA+U Calculations

The normal spinel cobalt oxide Co3O4 is considered as a magnetic semiconducting material comprising of cobalt ions with two oxidation states of Co2+ and Co3+. Density Functional Theory (DFT) calculation are employed to generate the structural, electronic and optical properties using Generalized Gradient Approximation (GGA) function. The Perdew-Burke-Ernzerh for solids (PBEsol) exchange-correlation functional approach successfully predict the semiconductor behaviour of Co3O4 but severely underestimates the band gap in relation to the experimental value. The GGA+U is performed in order to treat the Co-3d states and achieve the band gap of 1.26eV which agrees with the experimental results. For optical studies, here we unveil the predicted three assumed electron transition occurring in Co3O4 for O(2p)→Co2+(t2g), O(2p)→Co3+(eg) and Co3+(t2g)→Co2+(t2g).

Conductivity dynamics of metallic-to-insulator transition near room temperature in normal spinel CoFe2O4 nanoparticles

Designing a ferrite with dual electrical characteristics: the effect of temperature and site occupancy on the conductivity mechanisms of spinel CoFe2O4.