Electronic and magnetic properties ofTi4O7predicted by self-interaction-corrected density functional theory

Abstract

Understanding electronic properties of sub-stoichiometric phases of titanium oxide such as Magnéli phase Ti 4 O 7 is crucial in designing and modeling resistive switching devices. Here we present our study on Magnéli phase Ti 4 O 7 together with rutile TiO 2 and Ti 2 O 3 using density functional theory methods with atomic-orbital-based self-interaction correction (ASIC). We predict a new antiferromagnetic ground state in the low temperature phase (or LT phase), and we explain energy difference with a competing antiferromagnetic state using a Heisenberg model. The predicted energy ordering of these states in the LT phase is calculated to be robust in a wide range of modeled isotropic strain. We have also investigated the dependence of the electronic structures of the Ti-O phases on stoichiometry. The splitting of titanium t 2g orbitals is enhanced with increasing oxygen deficiency as Ti-O is reduced. The electronic properties of all these phases can be reasonably well described by applying ASIC with a 'standard' value for transition metal oxides of the empirical parameter α of 0.5 representing the magnitude of the applied self-interaction correction.

Influence of precursor type on structural, morphological, dielectric and magnetic properties of TiO2 nanoparticles

“…1b), the present phase was only anatase with characteristic planes (101), (004), (200), (105), (211) [29], which is a new finding in this work at this temperature. The intensity of peaks corresponding to anatase increased at this temperature indicating improved crystallization of anatase phase.…”

Quantum Monte Carlo analysis of a charge ordered insulating antiferromagnet: the Ti4O7 Magnéli phase

“…Using LDA+U, LDA+SIC, or the HSE06 hybrid functional, the AF states are stable but the difference in energy is only 4 -5 meV per formula unit. In previous studies using LDA+U, 12 Table 2 shows the results of our DMC calculations of the energies of the FM, AF1, and AF3 states, as well as the energies from LDA+U, LDA+SIC 28 using α = 0.5, and also from HSE06 hybrid functional; 28 Table 3 shows the energy gaps obtained from LDA+U, LDA+SIC calculations (α = 0.5), and HSE06 hybrid functional. We note that neither the U-parameter in LDA+U or the α-parameter in LDA+SIC in our calculations was adjusted to fit the energy gaps.…”

“…Leonov et al 12 performed an LDA+U calculation on the low temperature phase of Ti 4 O 7 and found an energy gap in good agreement with experiment and an antiferromagnetic (AF) charge-ordered ground state; Eyert et al 25 performed LDA band structure calculation on the same low temperature structure but were unable to reproduce the spin-singlet ground state. More recently, Liborio et al 26 In a more recent study, X. Zhong et al 28 suggested two energetically competing low-energy anti-ferromagnetic states at low temperature using an atomic self-interaction correction (SIC) scheme within DFT implemented in the SIESTA 29 electronic structure code, as well as more expensive hybrid functional (HSE06) 30,31 all-electron calculations. One state was the previously studied AF state by Liborio et al, 26 while the other one was a new AF state with lower energy.…”

The effect of a Ta oxygen scavenger layer on HfO2-based resistive switching behavior: thermodynamic stability, electronic structure, and low-bias transport

“…GGA+U and other advanced DFT methods such as hybrid functionals and Self-Interaction Corrections (SIC) systematically alleviate the problems of underestimating semiconductor band gaps [19][20][21][22]. We use norm-conserving pseudopotentials [23] and a plane wave cut-off at 400 Ry; a 2×2×1 k-point sampling is used for geometry relaxation and transport calculations.…”