Tian Decheng

A Raman study of the ring defects in GeO2-SiO2 glasses

The Raman spectra of GeO2-SiO2 glasses have been studied using samples of different GeO2 contents, which are found to have the general features of the spectrum of vitreous SiO2(v-SiO2). It is demonstrated that substitution of Ge for Si in the v-SiO2 network prevents the formation of ring structures. A new vibrational band located at 570-700 cm-1 was found in the spectra of high-GeO2-content samples (above 5.0 at.%GeO2). It is also shown that the W3 vibration of the v-SiO2 network is reduced in highly GeO2 doped GeO2-SiO2 glasses.

Darboux transformation method for solving the sine-gordon equation in a laboratory reference

The sine-Gordon equation is solved in a laboratory reference using the method of Darboux transformation. Using the Liouville theorem, explicit expressions of the single soliton solution and the breather solution are derived from the Darboux matrix in the case of a null spectral parameter.

Possible Evidence for Superlocalization on Fractal Network from the Thermopower Data

The theory for the thermoelectric power in the variable-range hopping is extended to the fractal regime where the wavefunctions of the electronic states are superlocalized. The thermopower is shown to scale as T-D/(D+C), where D is the fractal dimension and zeta the superlocalization exponent. Recent thermopower data on doped polyacetylene samples are examined and it is found that their temperature dependence agrees with the present theory. The superlocalization exponent obtained is consistent with existing theory and numerical results. We demonstrate that the data can be regarded as evidence for the superlocalization on fractal network.

Electronic structure of bismuth molybdenum oxide single crystal Bi0.19MoO3

Single crystal Bi0.19MoO3 has been grown by the fused salt electrolytic technique. X-ray powder diffraction shows that the unit cell parameters are: a=1.9985nm, b=0.4085nm and c=1.4437nm. The temperature dependence of resistivity demonstrates a semiconductor characteristic. X-ray photoemission spectroscopy studies show that the valence bands of Bi0.19MoO3 are made up of oxygen p? and the ?*, ? and ? bonding bands formed by orbital combination. The shoulder at 0.4eV near the top of the valence band may be formed from the non-bonding dxy orbitals of some Mo atoms. The O1s core-electron spectrum reveals the presence of two inequivalent bonds of oxygen ions in Bi0.19MoO3. The Bi4f core-level spectrum shows two bonding characters of Bi atoms in bismuth molybdenum oxide single crystals. The Mo3d core-level spectrum could be decomposed into two types of valence states of molybdenum(Mo+5 and Mo+6).

An anisotropic model of sandpile

An anisotropic model of sandpile has been proposed with different topping in different directions taken in consideration. Simulation results show that no significant differences exist between this anisotropic model and the isotropic one.

Real-Space Renormalization Group Approach of the Potts Model on the Octagonal Quasi-Periodic Tiling

A one-step real-space renormalization group (RSRG) transformation is used to study the ferromagnetic (FM) Potts model on the two-dimensional (2D) octagonal quasi-periodic tiling (OQT). The critical exponents of the correlation length in theq=1,2,3,4 cases and the crtitical surface of the Ising model are obtained. The results are discussed by comparing with previous results on the OQT and the square lattice (SQL).

Thermodynamic properties of the charge-density-wave transition in potasium blue brone

Thermodynamic properties of the charge-density-wave (CDW) transition in potassium blue bronze K0.3MoO3 are investigated by the measurement of specific heat. A second-order phase transition is observed at 177.5 K. The specific heat jump, and enthalpy and entropy changes associated with the transition are estimated. The results suggest that the lattice plays an important role in thermodynamics for this compound. Analysis of the data near CDW transition shows that width of critical region is about 6 K and the critical behavior belongs to the universality class of the three-dimensional XY model.

Study of experimental electronic structure of bidimensional semiconductor red bronze K0.33MoO3

X ray photoemission spectra measurements were carried out to elucidate the valence band picture and bonding characters of the two dimensional semiconductor red bronze K0.33MoO3. The valence band spectrum is similar to that of measurement of UPS, and in agreement with the molecular orbital model presented by Travaglini. Asymmetric and broadening line shape of O-1s means the presence of several inequivalent bonds of oxygen. Mo-3d core-level spectrum reveals that there are two kinds of valence states of molybdenum (Mo+5, Mo+6), and that its average valence state is +5.42.

SCALING AND SCALING-RELEVANT DYNAMICAL PROPERTIES OF PENROSE TILING

The scaling and the scaling-relevant spectral properties of Penrose tiling are investigated. The fractal dimension d(f) of this tiling is analytically obtained, which is two, equal to its Euclidean dimension. Similar to usual self-similar structure, the vibrational density of states for Penrose lattice is also found to follow a power law rho(omega) similar to omega(ds-1) with spectral dimension d(s) = 2, which accounts for a special vibrational excitation in quasicrystals: the fracton-like excitation, whose state is critical. The simulation of random walk on this Penrose lattice indicates that the diffusive dimension d(w) = 2, thus the relation d(s) = 2d(f)/d(w) holds.

Diffusion-Limited Aggregation of Dimers

We have simulated the diffusion-limited growth of dimers on a two-dimensional triangular lattice and have found that if tips of the dimers have different polarities, the resulting clusters, due to the alignment of the dimers and polarities chosen, are less dense than the clusters generated without polarities. These results make our model an effective way to demonstrate the role of the sticking probabilities in the diffusion-limited aggregation.