Influence of Molecular Orbitals on Magnetic Properties of [x

Alexey O Shorikov,Sergey V Streltsov,Vladimir I Anisimov,Alexander I Poteryaev,Sergey L Skornyakov

doi:10.3390/molecules25092211

Abstract

Recent discoveries of various novel iron oxides and hydrides, which become stable at very high pressure and temperature, are extremely important for geoscience. In this paper, we report the results of an investigation on the electronic structure and magnetic properties of the hydride FeOH, using density functional theory plus dynamical mean-field theory (DFT+DMFT) calculations. An increase in the hydrogen concentration resulted in the destruction of dimeric oxygen pairs and, hence, a specific band structure of FeO with strongly hybridized Fe--O- anti-bonding molecular orbitals, which led to a metallic state with the Fe ions at nearly 3+. Increasing the H concentration resulted in effective mass enhancement growth which indicated an increase in the magnetic moment localization. The calculated static momentum-resolved spin susceptibility demonstrated that an incommensurate antiferromagnetic (AFM) order was expected for FeO, whereas strong ferromagnetic (FM) fluctuations were observed for FeOH.

Highlights

In the study of the formation of molecular orbitals, organic compounds are prominent
We carried out the DFT and DFT+DMFT calculations of the electronic and magnetic properties of the stoichiometric FeO2 and FeO2 Hx series for a number of hydrogen concentrations
The analysis of the DFT DOSes revealed that hydrogen doping destroyed the dimeric O–O pair and resulted in a complete reorganization of the band structure near the Fermi level: the broad peak corresponding π to the Fe eπ g -O pz hybridization band vanished and the whole width of the e g band decreased almost twice

Summary

Introduction

In the study of the formation of molecular orbitals, organic compounds are prominent. Iron is in the oxygen octahedra; they share their corners, and some of the oxygens form dimer-like structures. These dimeric O atoms and formed molecular orbitals were shown to play a crucial role and strongly affect the valence state of Fe, and the electronic structure and magnetic properties of FeO2 [12]. In contrast to the sister compound, FeS2 , iron dioxide was predicted to be a “bad metal” with a pseudogap at the Fermi level, a paramagnet with unusual—for transition metal oxides—temperature behaviour of the magnetic susceptibility (increasing with temperature) and unexpected valencies of the Fe and dimeric O–O pair, which are, intensively debated at present [10,12,13]. The present paper aims to fill this gap in the understanding of the electronic and magnetic structure of nonstoichiometric FeO2 Hx

Structural Properties

GGA-PBE Band Structure

Conclusions