We introduce an effective model for e(g) electrons to describe quasi-two-dimensional layered La(2-x)Sr(x)NiO(4) nickelates and study it using correlated wavefunctions on 8 × 8 and 6 × 6 clusters. The effective Hamiltonian includes the kinetic energy, on-site Coulomb interactions for e(g) electrons (intraorbital U and Hund's exchange J(H)) and the coupling between e(g) electrons and Jahn-Teller ...

111 sitzr measurements of the Ni and Co K-edge XAFS spectra of Li1.~Ni02 and Lil.,CoOz as a function of x were successfully carried out for the first time using an electrocl~emical ceii. It is observed that a local Jahn-Teller distortion of the Ni06 octahedron in LiN102 was reduced with deintercalation of Li which caused oxidatiou of the Jahn-Teller d7 ~ i ~ * ion to do Ni4+i011. A substitution...

Theoretical calculations are performed for the X2E"2 and A 2E"3 states of the cycloheptatrienyl (tropyl) radical C7H7. An important goal of these calculations is to predict and to guide the analysis of the experimentally observed A 2E"3-X 2E"2 electronic spectrum. Vibrational frequencies of the tropyl radical at the conical intersection and stationary points of its X and A state Jahn-Teller dis...

We report on the optical properties of the hole-doped manganites Nd0.7Sr0.3MnO3, La0.7Ca0.3MnO3, and La0.7Sr0.3MnO3. The low-energy optical conductivity in the paramagnetic-insulating state of these materials is characterized by a broad maximum near 1 eV. This feature shifts to lower energy and grows in optical oscillator strength as the temperature is lowered into the ferromagnetic state. It r...

The electronic structure of YMnO3 in its highand low-temperature hexagonal phases has been investigated within the local spin-density approximation (LSDA) and by the LSDA + U method which takes into account the local Coulomb interaction between d electrons of transitionmetal ions. In contrast to the case for orthorhombic manganites, the d4-configuration degeneracy is already lifted in the high-...

The temperature-dependent structural changes were investigated by using the X-ray diffraction and the Extended X-ray absorption fine spectroscopy (EXAFS) for layered perovskite manganites La2-2xSr1+2xMn2O7 (x=0.33 and 0.4). The anomalous changes of Mn-O bond length and Jahn-Teller (J-T) distortion of MnO6 octahedron were observed, corresponding to ferromagnetic transition temperature (~ 120 K)....

Na2C60 is believed to be an electron-hole counterpart of the Mott-Jahn–Teller insulator A4C60 salts. We present a study of infrared, ESR, NMR spectroscopy, X-ray diffraction, chemical composition and neutron scattering on this compound. Our spectroscopic results at room temperature can be reconciled in a picture of segregated, separate regions of the size 3–10 nm. We observe a significant insul...

The recent cavity ringdown (CRD) measurement of the forbidden à 2E ← X̃ A2 transition of the nitrate radical NO3 reveals a rich, well-resolved spectrum in the near-infrared. The spectroscopic detail provides a new window onto the Jahn–Teller (JT) and pseudo-Jahn–Teller (PJT) effects in NO3. This paper reviews the current experimental evidence for vibronic coupling in the à state and discusses th...

The single-crystal X-ray structure of the single-molecule magnet [Mn12O12(O2CC6H4-2-CH3)16(H2O)4] Æ CH2Cl2 Æ 2H2O (complex 1) is reported. Complex 1 is a new example of a ‘‘Jahn–Teller isomer’’, since it has two Mn(III) ions with abnormally oriented Jahn–Teller elongation axes. Complex 1 has a lower activation energy (Ueff = 29 K) for magnetization reversal relative to other reported [Mn12O12] ...