2014 Recent experimental results obtained on A15 compounds allow a better understanding of the correlation between superconductivity and lattice instability in this system. The effect of the lattice distortion is shown to reduce the superconducting transition Tc. An enhancement of Tc in the case of V3Si is obtained when the temperature of the martensitic transition is lowered (by pressure or de...

Recently we discussed the Renner-Teller effect in triatomic molecules [J. Chem. Phys. 125, 094102 (2006)]. In that article the main message is that the Renner-Teller phenomenon, just like the Jahn-Teller phenomenon, is a topological effect. Now we extend this study to a tetra-atomic system, namely, the C(2)H(2) (+) ion, for which topological effects are revealed when one atom surrounds the tria...

Ab initio calculations are performed for the X̃2E′′ 1 and à 2A′′ 2 states of the cyclopentadienyl radical. An important goal of these calculations is to guide the analysis of the experimentally observed Ã2A′′ 2 -X̃ 2E′′ 1 electronic spectrum. Vibrational frequencies for both the X̃ and à state are reported. Large changes

The laser excited, jet-cooled Ã2A′′ 2 − X̃2E′′ 1 electronic spectrum of the cyclopentadienyl radical yields detailed information about the vibronic structure of both its à and X̃ states. A straight-forward assignment of the à vibronic structure is presented. The X̃ state vibronic structure reveals a comprehensive picture of the Jahn-Teller distortion of its potential energy surface. The molecular ...

We show that complex Lie algebras (in particular sl(2,C)) provide us with an elegant method for studying the transition from real to complex eigenvalues of a class of non-Hermitian Hamiltonians: complexified Scarf II, generalized Pöschl-Teller, and Morse. The characterizations of these Hamiltonians under the so-called pseudoHermiticity are also discussed. PACS: 02.20.Sv; 03.65.Fd; 03.65.Ge

A general formalism for constructing configuration localized states for one-dimensional potentials is presented. It allows the evaluation of accurate approximations to the vibrational matrix elements of the momentum operator and of arbitrary functions of the coordinate. The formalism is applied to three potentials of interest in molecular physics: the harmonic oscillator, Morse, and Pöschl-Tell...

X-ray-absorption fine-structure measurements from the Mn and La K edges of samples of La12xCaxMnO3 (x50→1) are presented as a function of temperature. In the insulating state, distortions of the Mn-O environment are found to be linear with calcium concentration x . These distortions are consistent with a model where individual Mn sites have strong Jahn-Teller ~JT! distortions while Mn sites do ...

Narrow-band conductors may turn insulating and magnetic as a consequence of strong electron-electron correlation. In molecular conductors, the concomitance of a strong Jahn-Teller coupling may give rise to the alternative possibility of a non-magnetic insulator, with or without a static cooperative Jahn-Teller distortion. In the latter case the insulator has Mott-like properties, with an intere...

The historical development and theories explaining the Verwey transition in Magnetite are discussed. An overview of current experimental work is included. Also examined are multiple charge ordering theories and more sophisticated considerations of Jahn-Teller effects which attempt to explain this long-standing problem in strongly-correlated electron systems.

A new lithium vanadium fluoride Li2VF6 was prepared by reacting lithium fluoride LiF with vanadium tetrafluoride VF4 in a monel capsule at 500 ◦C. The crystal structure has been determined by means of powder X-ray diffraction. Trirutile-type dilithium hexafluorovanadate(IV) crystallizes in the tetragonal space group P42/mnm with lattice parameters a = 459.99(1), b = 459.99(1), c = 896.64(2) pm....