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Spin lattice relaxation time of 1 H in a charge-transfer complex of bisethylenedioxytetrathia fulvalene (BO) and decyltetracyanoquinodimethane (C 10 TCNQ) has been measured in a low-temperature region of 2–50 K. The relaxation rate at the resonance frequency of 9.5 MHz exhibits Korringa-like behavior down to about 30 K. At lower temperatures, it exhibits a substantial increase with a peak at around 5 K and then rapidly decreases with decreasing temperature. Similar behavior is observed in the relaxation rate at a higher frequency (15 MHz), but the increase is supressed by a higher external field. These behaviors are well explained by the theory of localization in weakly disordered systems. These results indicate that at low temperatures, Anderson localization is detected in BO conductive layers.

Structures of Langmuir-Blodgett (LB) superlattice films formed with alternately deposited fatty acid Cd salts with different alkyl-chain length are studied by high resolution X-ray diffraction method using a synchrotron radiation source. The remarkable diffraction peak shift is observed in the superlattice film. The shift is interpreted in terms of the Guinier effect in partially-disordered superlattice system. Simultaneous modulation of molecular position and of molecular scattering factor results in the peak shift. The effect of alkyl-chain species substitution and of cooling on the peak shift are also described. The partial disorder in the superlattice is caused by dissolution of LB film.

A comparative study of the multiplet energies of the isoelectronic 3d3 ions in MgO host crystal using the first-principles calculation has been performed by discrete-variational multi-electron method. In this investigation, the effect of lattice relaxation was considered based on geometry optimization using first-principles band-structure calculation. The spin-polarization effect and the effect of Hubbard U were also investigated. The estimated multiplet energies were reasonably well reproduced when we used the optimized cluster with spin-polarization effect and some corrections such as configuration dependent correction and correlation correction. The results also show that the lattice relaxation is important to reproduce the tendency of the transitions from 4A2 state to 4T2 and 4T1a states, while the tendency of the transition from 2E state to 4A2 state is mainly determined by the effect of electron correlation.

First-principles configuration–interaction (CI) calculations of the multiplet structures and the ground-state (GS) absorption spectra of isoelectronic 3d 3 ions such as V 2+ , Cr 3+ , and Mn 4+ in α-Al 2 O 3 have been performed. The results of the molecular orbital (MO) calculations without lattice-relaxation effect indicated that the GSMOs are not appropriate for the calculation of the absorption spectra in the case of V 2+ in α-Al 2 O 3 (α-Al 2 O 3 :V 2+ ) due to the strong mixing between the V 3d orbitals and the conduction band. Therefore we investigated the effect of orbital-relaxation by tentatively performing CI calculations using MOs obtained for several excited states and the CI calculation using the MOs in the intermediate t 2 g 1.5 e g 1.5 configuration was found to give reasonable theoretical spectra. The theoretical peak energies and the relative peak intensities were improved further for α-Al 2 O 3 :V 2+ and α-Al 2 O 3 :Cr 3+ by consideration of energy corrections such as configuration-depen...

In this paper, we investigated the 4 f –5 d absorption spectrum of Ce 3+ in LiYF 4 based on first-principles calculations. In order to take into account the effect of lattice relaxation, the local structure around Ce 3+ was optimized based on a pseudopotential plane wave method using the CASTEP code. The scalar relativistic effects were taken into account in this calculation. The results indicated that the position of Ce 3+ was shifted to an off-center position along c -axis by 0.074 A, resulting in a symmetry reduction of Ce 3+ site from S 4 to C 2 . In order to calculate the theoretical absorption spectra, the fully-relativistic four-component molecular orbital (MO) calculations were also performed using a cluster model constructed from the optimized structure. The theoretical 4 f –5 d absorption spectrum of Ce 3+ in LiYF 4 obtained for the optimized structure was in good agreement with the experimental one. Especially the five peaks in the experimental spectrum were reproduced without any empirical par...