Structural Phase Transitions Induced by a Pseudo-Jahn-Teller Effect

1973 ◽  
Vol 7 (2) ◽  
pp. 894-897 ◽  
Author(s):  
B. Halperin
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Teller Effect ◽  
Structural Phase Transitions ◽  
Jahn Teller ◽  
Jahn Teller Effect

Cooperative Pseudo Jahn-Teller Effect as Microscopic Mechanism of (OMT)-(LTT) Structural Phase Transition in La2−xBaxCuO4Superconductors

1992 ◽  
Vol 291 ◽  
Author(s):  
Michael D. Kaplan
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Electronic States ◽  
Teller Effect ◽  
Excited Electronic States ◽  
Microscopic Mechanism ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Local Distortions

ABSTRACTA microscopic mechanism for the structural phase transition from the orthorhombic mediate temperature (OMT) phase into the low temperature tetragonal (LTT) one is suggested on the basis of the cooperative pseudo Jahn-Teller effect. The local distortions mixing the ground and the first excited electronic states are ordered antiferrodistortively and are connected in part, with the oxygen octahedra rotations around the [100] axis. The results are in agreement, with the neutron scattering experiments data.

Phase diagrams of Ni2+xMn1-xGa Heusler alloys from Hubbard Hamiltonian with account of Jahn-Teller effect

2011 ◽  
Vol 1310 ◽  
Author(s):  
Mikhail A. Zagrebin ◽  
Vasiliy D. Buchelnikov ◽  
Sergey V. Taskaev ◽  
Natal’ya Yu. Fedulova
Keyword(s):  
Phase Diagram ◽  
Free Energy ◽  
Phase Transitions ◽  
Phase Diagrams ◽  
Density Of States ◽  
Heusler Alloys ◽  
Teller Effect ◽  
Hubbard Hamiltonian ◽  
Jahn Teller ◽  
Jahn Teller Effect

ABSTRACTIn this work a microscopic Hamiltonian is investigated using the Hubbard model for a ferromagnet with two degenerate bands, taking into account the Jahn-Teller effect. A macroscopic free energy is obtained from the microscopic Hubbard Hamiltonian. All free energy coefficients depend on microscopic parameters: temperature T and composition x. As a result of analytical minimization of free energy, phase diagrams are numerically constructed. It is shown that at certain values of parameters on the phase diagrams there are thermodynamic paths which correspond to experimentally observed sequences of phase transitions. Using density of states spectra for different compositions x the T-x phase diagram is numerically constructed. This phase diagram can theoretically explain experimentally observed behavior of the temperatures of phase transitions.

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