نتایج جستجو برای: jahn
تعداد نتایج: 1797 فیلتر نتایج به سال:
The ground and electronically excited states of cyclic N(3) (+) are characterized at the equilibrium D(3h) geometry and along the Jahn-Teller distortions. Lowest excited states are derived from single excitations from the doubly degenerate highest occupied molecular orbitals (HOMOs) to the doubly degenerate lowest unoccupied molecular orbitals (LUMOs), which give rise to two exactly and two nea...
Competing Jahn-Teller distortions combined with geometrical frustration give rise to a rich phase diagram as a function of x(Cu) and temperature in the spinel system Ni1xCuxCr2O4. The Jahn-Teller distortion of the end members acts in opposite ways with an elongation of the NiO4 tetrahedra resulting in a structural transition at TS1 = 317 K in NiCr2O4, but a flattening in the CuO4 tetrahedra at...
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...
The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller...
Alkali-doped fullerides show a wide range of electronic phases in function of alkali atoms and the degree of doping. Although the presence of strong electron correlations is well established, recent investigations also give evidence for dynamical Jahn-Teller instability in the insulating and the metallic trivalent fullerides. In this work, to reveal the interplay of these interactions in fuller...
Using first-principles density-functional calculations, we explore the possibility of magnetic order at the rebonded DB step of the Si(001) surface. The rebonded DB step containing threefold coordinated Si atoms can be treated as a one-dimensional dangling-bond (DB) wire along the step edge. We find that Si atoms composing the step edge are displaced up and down alternatively due to Jahn-Teller...
A survey of ligand eld theory is given and the possibility of ob serving the Jahn Teller e ect in molecules by means of gas phase elec tron di raction is discussed The theory of the dynamic Jahn Teller e ect is outlined and theoretical and experimental results for VCl are reviewed In H A Jahn and E Teller predicted that a nonlinear molecule which is in a degenerate state will seek to change its...
Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above T c is a major challenge for all unconventional superconductors. The molecular A3C60 fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C60 (3-) electronic structure controls the geometry and spin state...
In a two orbital double exchange model we formulate Jahn-Teller coupled charge density wave in half-filled limit. Softening of Jahn-Teller phonons corresponding to distortion modes Q2 or Q3 associated with perfect nesting of Fermi surface leads to this instability at low temperature. The gap equation for charge density wave state and its dependences on electron-lattice coupling are calculated e...
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