We use the temperature of the structural phase transition to determine the Jahn-Teller (JT) coupling constant in the model derived for LaMnO3 which includes both the superexchange between S = 2 spins and the JT effect. We also investigate the dependence of the exchange constants on the value of the on-site Coulomb element U , and on the orbital ordering. Journal ref.: O. Sikora and A. M. Oleś, ...

A model interaction is proposed in which pairing is caused by a non-local Jahn-Teller (JT)-like instability due to the coupling between planar O states and k = 0 phonons. Apart from pairing, the interaction is found to naturally allow metallic stripe formation. The consequences of the model for supercon-ductivity in the cuprates are discussed. The model is shown to be consistent with numerous s...

A cluster Monte Carlo algorithm for the Ashkin-Teller (AT) model is constructed according to the guidelines of a general scheme for such algorithms. Its dynamical behaviour is tested for the square lattice AT model. We perform simulations on the line of critical points along which the exponents vary continuously, and find that critical slowing down is significantly reduced. We find continuous v...

using different DFT methods including B3LYP/6-31G(d), VWN/6-31G(d), PBE/TZP and PBE/6-31G(d) shows that, contrary to C60 , which prefers D5d symmetry, the ground state of B80 + adopts S6 point group symmetry. A D3d structure is identified as a saddle point among the S6 minima of B80 . The distortion of D3d to S6 in B80 + is attributed to a superposition of Jahn–Teller and pseudo-Jahn–Teller eff...

We show that the presently available data on the Gamow-Teller (GT) strength in mid-f p-shell nuclei are proportional to the product of the numbers of valence protons and neutron holes in the full f p-shell. This observation leads to important insights into the mechanism for GT quenching and to a simple parametrization of the Gamow-Teller strengths important for electron capture by f p-shell nuc...

The topology of the ground-state potential energy surface of M(CN)(6) with orbitally degenerate (2)T(2g) (M = Ti(III) (t(2g)(1)), Fe(III) and Mn(II) (both low-spin t(2g)(5))) and (3)T(1g) ground states (M = V(III) (t(2g)(2)), Mn(III) and Cr(II) (both low-spin t(2g)(4))) has been studied with linear and quadratic Jahn-Teller coupling models in the five-dimensional space of the epsilon(g) and tau...

Background: Electron-capture reaction rates on medium-heavy nuclei are an important ingredient for modeling the late evolution of stars that become core-collapse or thermonuclear supernovae. The estimation of these rates requires the knowledge of Gamow-Teller strength distributions in the β+ direction. Astrophysical models rely on electron-capture rate tables largely based on theoretical models...

Recently it has been shown that pseudospin symmetry has its origins in a relativistic symmetry of the Dirac Hamiltonian. Using this symmetry we relate single nucleon relativistic magnetic moments of states in a pseudospin doublet to the relativistic magnetic dipole transitions between the states in the doublet, and we relate single nucleon relativistic Gamow Teller transitions within states in ...

Using the coupled cluster method ~CCM!, we present a simple accurate calculation for the energies of the groundand first excited states of the linear E ^ e Jahn–Teller and pseudo-Jahn–Teller Hamiltonians. From the solution of a single transcendental equation, we obtain results with a maximal error of 1.2%. These results are notably better than previous results obtained both via the CCM and othe...

A visual scientist might be considered successful for making inroads into one problem area. Davida Teller stood out for at least three: her contributions to models of visual detection and discrimination, to theoretical discussions of psychophysical linking hypotheses, and to the creation of the modern science of visual development in infants. She received multiple honors, including the Friedenw...