Chuji Horie

Phonon Dispersion Relations of Graphite

Phonon dispersion relations of graphite are calculated by using the Born-von Karman force constant model. Eight force parameters are introduced to take anisotropic properties of graphite into account, and are determined so as to fit available experimental data including a new finding that A 2u out of plane mode occurs at 868 cm -1 .

Magnetic properties of amorphous Co-R (R = Sm, Nd, Pr) alloys☆

Abstract Measurements of magnetization and susceptibility were carried out in the temperature range from 4.2 to 300 K for amorphous Co 100- x R x (R = Sm, Nd, Pr; 50 ⩽ x ⩽ 70) alloys prepared by a rapid quenching technique. The magnetic properties of these amorphous alloys are discussed based on a local moment model. It is concluded that the rare earth R in the amorphous alloys behaves as trivalent positive ions, and that the magnitude of effective magnetic moment inherent in Co ion decreases with an increase of x and almost vanishes around x = 60.

Lattice dynamics of first-stage alkali metal graphite intercalation compounds

Abstract Phonon dispersion relations for first-stage alkali metal graphite intercalation compounds C 8 M (M = K, Rb) are calculated by using the Born-von Karman force constant model. The characteristic effect of intercalation is revealed by comparing the phonon dispersion relation for C 8 M with that for graphite folded into the Brillouin zone of C 8 M. Among fifty-four normal modes for C 8 M, forty-eight modes are associated with vibrations of carbons and exhibit a definite correspondence with the folded dispersion curves for graphite, The remaining six optical modes, which originate from vibrations of alkali metal atoms, yield a significant perturbation to acoustic modes. Experimental results of the Raman scattering for C 8 M are discussed on the basis of the dispersion relations obtained.

4f related resonant photoemission spectra of Ce metals

Abstract The characteristics features observed in BIS, UPS and/or XPS of Ce metals are explained by using a Hamiltonian which includes the Anderson-like mixing term with spin-orbit splitting and degeneracy of the 4f1 level explicitly considered. The photon-energy dependence of the 4d-4f resonant photoemission spectrum is also interpreted.

Interlayer Stacking Structure in First Stage Alkali Binary and Ternary Graphite Intercalation Compounds

Order-order and/or order-disorder transitions associated with changes of intercalate interlayer stacking sequences in stage-1 alkali graphite intercalation compounds are studied within a framework of mean-field lattice gas model. The species dependence of the interlayer stacking phases and phase transitions in binary compounds MC 8 (M=K, Rb, Cs) as well as in ternary compound KCsC 16 is described in terms of the present lattice gas model.

STM Images of Graphite Dependent on Size of the Tip

A simple model is presented to investigate the effect of the size of the tip in a scanning tunneling microscope on the image of graphite. In the model, the tip and carbon atoms of the surface of graphite are replaced by circles with areas effective to the local tunneling currents. It is shown that the STM images reflect the hexagonal arrangement of carbons but differ depending on the size of the tip.

Theory of Pressure-Induced Staging Transitions in Graphite Intercalation Compounds

Theory is presented of the mechanism of pressure-induced staging transitions in alkali-metal graphite intercalation compounds (A-GICs). The most stable stoichiometry at T =0 K is determined for various species of intercalant atoms. Effect of pressure is taken into account by varying the distance between the two graphite layers which sandwich an intercalant layer. Lithium GICs are found to be stable with the stoichiometry of LiC 6 × n , where n is the stage number, at all pressures. The most stable stoichiometry of heavy alkali-metal GICs is shown to be MC 14 × n at ambient pressure, but MC 8 × n at higher hydrostatic pressure. Comparison is made of the theoretical results with the experimental ones at finite temperatures.

Condensation of Excitons in a Highly Excited State of Semiconductors

The condensation of excitons in a highly excited state of semiconductors or insulators is investigated without an assumption of excitons being bosons. The discussion is based on the quasi-chemical equilibrium theory and the dynamical correlation between electrons and/or holes is taken into account with an appropriate screening parameter. It turns out that the concentration of excitons in the ground level attains a finite value when n exc exceeds a value n exc c which is identical to the critical concentration for the Bose-Einstein condensation in an ideal boson system. It is also seen that the excitons can be treated as bosons for n c n exc c . It is also mentioned how to determine the concentration of free pairs and of excitons against the total concentration of excited pairs. A favorable situation for the observation of the exciton condensation is also discussed.

Fine resolution of energy structures of large molecules in solution by coherent population-grating spectroscopy

We have succeeded in observing finely resolved spectra in the spectral regions of absorption and emission bands of cresyl violet in ethanol, by means of population-grating spectroscopy based on four-photon parametric mixing. The inhomogeneous width is investigated in terms of the excitation frequency dependence. The energy separation and the homogeneous width are also analyzed by assuming that the observed fine bands consist of several Lorentzian lines. It is revealed that the observed spectra reflect the detailed vibrational and vibronic structures of molecules. This high-resolution spectroscopy can be readily applied to more general disordered systems in the condensed phase.

Formation of strongly correlated f bands

Abstract A cumulant-expansion theory starting from the atomic limit is presented for intermediate-valence compounds. It is elucidated how the formation of f bands is controlled by dynamical fluctuations of spin and charge. The infrared conductivity calculated is in good agreement with experimental results in CePd 3 .