We discuss Mott insulating and metallic phases of a model with eg orbital degeneracy to understand physics of Mn perovskite compounds. Quantum Monte Carlo and Lanczos diagonalization results are discussed in this model. To reproduce experimental results on charge gap and Jahn-Teller distortions, we show that a synergy between the strong correlation effects and the Jahn-Teller coupling is import...

Starting from a spin-orbital model for doped manganites, we investigate a competition between ferromagnetic and antiferromagnetic order in a one-dimensional model at finite temperature. The magnetic and orbital order at half filling support each other and depend on a small antiferromagnetic superexchange between t2g spins and on an alternating Jahn-Teller potential. The crossover to a metallic ...

Total scattering based atomic pair distribution function (PDF) analysis, with the advent of high data throughput neutron powder diffractometers, helps understanding the nature of the Jahn-Teller (JT) phase transition in La1-xCaxMnO3 colossal magnetoresistive (CMR) manganites. The JT distortion of the MnO6 octahedra, is long-range ordered in the orthorhombic (O) phase, but disappears in the pseu...

The potential energy surfaces of the group 17 XF3 (X = Cl, Br, I, At) fluorides have been investigated for the first time with multiconfigurational wave function theory approaches. In agreement with experiment, bent T-shaped C(2v) structures are computed for ClF3, BrF3, and IF3, while we predict that an average D(3h) structure would be experimentally observed for AtF3. Electron correlation and ...

Jahn-Teller (JT) electron-phonon coupling effects in the colossal magnetoresistance perovskite compounds La1−xAxMnO3 are investigated. Electronelectron correlations between two degenerate Mn eg orbitals are studied in the Gutzwiller approximation. The static JT distortion and antiadiabatic polaron effects are studied in a modified Lang-Firsov approximation. We find that (i) the electron or hole...

The 11B(3He, t), 11B(d, d), and 11B(p, p) reactions were measured at forward scattering angles including 0 to study the isovector and isoscalar spin-flip M1 strengths in 11B. The measured 11B(3He, t) cross sections were compared with the results of the distorted-wave impulseapproximation (DWIA) calculation, and the Gamow-Teller (GT) strengths for low-lying states in 11C were determined. The GT ...