TY - JOUR
T1 - Covalency, double-counting, and the metal-insulator phase diagram in transition metal oxides
AU - Wang, Xin
AU - Han, M. J.
AU - De'Medici, Luca
AU - Park, Hyowon
AU - Marianetti, C. A.
AU - Millis, Andrew J.
PY - 2012/11/26
Y1 - 2012/11/26
N2 - Dynamical mean field theory calculations are used to show that for late transition metal oxides a critical variable for the Mott/charge-transfer transition is the number of d electrons, which is determined by charge transfer from oxygen ions. Insulating behavior is found only for a narrow range of d occupancy, irrespective of the size of the intra-d Coulomb repulsion. The result is useful in interpreting "density functional + U" and "density functional plus dynamical mean field" methods in which additional correlations are applied to a specific set of orbitals and an important role is played by the "double counting correction" which dictates the occupancy of these correlated orbitals. General considerations are presented and are illustrated by calculations for two representative transition metal oxide systems: layered perovskite Cu-based high-Tc materials, an orbitally nondegenerate electronically quasi-two-dimensional system, and pseudocubic rare earch nickelates, an orbitally degenerate electronically three-dimensional system. Density functional calculations yield d occupancies very far from the Mott metal-insulator phase boundary in the nickelate materials, but closer to it in the cuprates, indicating the sensitivity of theoretical models of the cuprates to the choice of double counting correction, and corroborating the critical role of lattice distortions in attaining the experimentally observed insulating phase in the nickelates. © 2012 American Physical Society.
AB - Dynamical mean field theory calculations are used to show that for late transition metal oxides a critical variable for the Mott/charge-transfer transition is the number of d electrons, which is determined by charge transfer from oxygen ions. Insulating behavior is found only for a narrow range of d occupancy, irrespective of the size of the intra-d Coulomb repulsion. The result is useful in interpreting "density functional + U" and "density functional plus dynamical mean field" methods in which additional correlations are applied to a specific set of orbitals and an important role is played by the "double counting correction" which dictates the occupancy of these correlated orbitals. General considerations are presented and are illustrated by calculations for two representative transition metal oxide systems: layered perovskite Cu-based high-Tc materials, an orbitally nondegenerate electronically quasi-two-dimensional system, and pseudocubic rare earch nickelates, an orbitally degenerate electronically three-dimensional system. Density functional calculations yield d occupancies very far from the Mott metal-insulator phase boundary in the nickelate materials, but closer to it in the cuprates, indicating the sensitivity of theoretical models of the cuprates to the choice of double counting correction, and corroborating the critical role of lattice distortions in attaining the experimentally observed insulating phase in the nickelates. © 2012 American Physical Society.
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U2 - 10.1103/PhysRevB.86.195136
DO - 10.1103/PhysRevB.86.195136
M3 - 21_Publication in refereed journal
VL - 86
JO - Physical Review B: covering condensed matter and materials physics
JF - Physical Review B: covering condensed matter and materials physics
SN - 2469-9950
IS - 19
M1 - 195136
ER -