Pressure-Driven Metal-Insulator Transition in Hematite from Dynamical Mean-Field Theory

Abstract

The local density approximation combined with dynamical mean-field theory is applied to study the paramagnetic and magnetically ordered phases of hematite Fe2O3 as a function of volume. As the volume is decreased, a simultaneous first-order insulator-metal and high-spin to low-spin transition occurs close to the experimental value of the critical volume. The high-spin insulating phase is destroyed by a progressive reduction of the spectral gap with increasing pressure, upon closing of which the high-spin phase becomes unstable. We conclude that the transition in Fe2O3 at approximately 50 GPa can be described as an electronically driven volume collapse.

Prediction of variation in d-orbital occupancy in strain induced tetragonal phase of BiFeO3 thin film

“…68 A lot of research work has been performed on this issue. [69][70][71][72][73] Also, there have been reports where calculations performed using the AMF functional showed the spin crossover from low to high spin states with the variation of parameter U. 66,67 Hence in order to get a complete insight about the electronic and magnetic properties of BFO in tetragonal (P4mm) phase, a series of calculations using the AMF and FLL functionals were performed by varying U from 2.72 eV to 10.88 eV while keeping J, constant to values ranging from 0.27 eV to 1.22 eV, as shown in Tables I-V respectively. For all the calculations performed using the AMF and FLL functionals given above in Tables I to V, it was observed that for the combination of parameters U=10.88 eV and J=0.27 eV, performed using the AMF functional gave S=1/2 spin state as given in Table I.…”

Magnetic collapse and the behavior of transition metal oxides at high pressure

“…In particular, this advanced theory makes it possible to determine the electronic structure and phase stability of paramagnetic correlated materials at finite temperatures, e.g., near a Mott insulator-metal transition [13][14][15][20][21][22][23][24][25][26][27][28]. The DFT+DMFT approach has been used to study the electronic and structural properties of correlated electron materials [11][12][13][14][15][16][17][18][19][20], including transition metal monoxides [22][23][24][25][26][27][28][29]. In practice, however, these calculations employed different approximations, resulting in various scenarios for the IMT.…”

“…This obstacle can be overcome by employing, e.g., a state-of-the-art method for calculating the electronic structure of strongly correlated materials [density functional plus dynamical mean-field theory (DFT+DMFT)] [9,10]. It merges ab initio band-structure techniques, such as the local density approximation (LDA) or the generalized gradient approximation (GGA), with dynamical mean-field theory (DMFT) of correlated electrons [9], providing a good quantitative description of the electronic and lattice properties [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In particular, this advanced theory makes it possible to determine the electronic structure and phase stability of paramagnetic correlated materials at finite temperatures, e.g., near a Mott insulator-metal transition [13][14][15][20][21][22][23][24][25][26][27][28].…”

“…It merges ab initio band-structure techniques, such as the local density approximation (LDA) or the generalized gradient approximation (GGA), with dynamical mean-field theory (DMFT) of correlated electrons [9], providing a good quantitative description of the electronic and lattice properties [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In particular, this advanced theory makes it possible to determine the electronic structure and phase stability of paramagnetic correlated materials at finite temperatures, e.g., near a Mott insulator-metal transition [13][14][15][20][21][22][23][24][25][26][27][28]. The DFT+DMFT approach has been used to study the electronic and structural properties of correlated electron materials [11][12][13][14][15][16][17][18][19][20], including transition metal monoxides [22][23][24][25...…”

Magnetism of iron and nickel from rotationally invariant Hirsch-Fye quantum Monte Carlo calculations

“…In accordance with this, recent LDA + DMFT calculations of correlated compounds also indicate that the magnetic transition temperatures appear to be significantly overestimated by using the density-density type of Coulomb interaction. 7,13,19 However, applications of these techniques so far have been mostly limited to simple model systems and only a few realistic calculations for 3d compounds have been recently presented. 20 This is mostly because of high computational costs (exponential with the number of orbitals) of these methods implemented with the full rotationally invariant Coulomb interaction which makes such calculations for 3d and 4f materials extremely expensive.…”