Impulsive stimulated thermal scattering (ISTS), a time-domain light scattering technique, provides a more than 6-decade time range from sub-ns to many ms. It permits characterization of the structural relaxation dynamics and determination of the relaxation strength or Debye-Waller factor in supercooled liquids, and thus allows testing of the mode coupling theory of the liquidglass transition. ISTS experiments were performed on glass formers salol, butylbenzene, and the molten salt [Ca(N03)]0.4[KNO3]0.6. The relaxational dynamics and the Debye-Waller factorfq=0 were obtained. A square-root anomaly was observed in fq=0 (T) at a crossover temperature Tc for all three materials, consistent with the prediction of mode coupling theory.

New experimental results obtained with various techniques on a less-studied glass-forming system are presented. At low frequency, a secondary βslow-process, decoupled from the viscous flow, is observed by 3 1P NMR. Raman scattering spectra and coherent neutron scattering spectra has been obtained in wide frequency and temperature ranges showing the same qualitative features for the Boson peak while the quasielastic contribution seems to differ markedly.

Quasi-elastic neutron scattering (NS) measurements of Salol have been carried out in order to study the α and β relaxations near the liquid-glass transition. The results are presented in the form of a susceptibility spectrum that is compared with the corresponding spectrum obtained from light scattering (LS) and with the predictions from the Mode Coupling Theory. The differences between the NS and LS results are due to the different correlators contributing to the susceptibility in the two types of scattering. The possible origin of these differences are discussed in the framework of the Mode Coupling Theory.

The structural relaxations of a dense, binary mixture of charged hard spheres are studied using the Mode Coupling Theory (MCT). Qualitative differences to non-ionic systems are shown to result from the long-range Coulomb interaction and charge ordering in dense molten salts. The presented non-equilibrium results are determined by the equilibrium structure, which is input using the well studied Mean Spherical Approximation.

We report measurements of the temperature and pressure dependence of ultrasonic modulus in polystyrene between 340 and 550 K and applied pressures up to 775 bar. The real and imaginary parts of the modulus are analyzed within the Havriliak-Negami model and very good agreement is found over the entire temperature and pressure ranges. Using the Vogel-Tammann-Fulcher equation for the relaxation time, the Kauzmann temperature TK and the fragility parameter D of polystyrene were determined. The value of D indicates that polystyrene is a fragile-glass former.

Thermal relaxation of glass structure has been studied on silica glasses densified by hot isostatic pressing. Density of the glasses relaxed toward the value of an undensified glass by thermal annealing. Relaxation rates of density of the glasses were measured after the annealing at several temperatures. Fast and slow relaxation processes were found from the analysis by using a stretched exponential relaxation function Φ(t)=exp{−(t/τeffβ}). The slow process becomes dominant after the fast process. Raman scattering spectrum also has been measured through the thermal relaxation. The width of the main band at 450cm−1 increased by the annealing and recovered the value for the undensified glass after the fast process. The bands at 1060 and 1200 cm−1 shifted back to the positions for the undensified glass. The high density state(Δρ/ρ∼0.5%), however, was maintained even after the fast process. From these results, it is deduced that the fast process is due to the recovery of the O3Si-O-SiO3 tilt angle and Si-O-Si bond angle to the mean values for the undensified glass.

Glass transition of of copper is simulated by the molecular dynamics method. Embedded atom method potential is used. The glass state was produced by quenching the liquid sample, which was produced by melting a crystal. The split second peak in RDF was observed in the glass state.

We have investigated the slow dynamics in the glass transition region of a supercooled liquid [Ca(NO3)2]0.4[KN3]0.6 by measuring the dynamic specific heat in the frequency range from 0.01 Hz to 5 kHz. The equilibrium dynamics of the system in this range is well described by the stretched exponential function, exp[-(t/τ)β], and the Vogel-Fulcher type relaxation time, τ = τ0exp[Δ/(T − T0)].

We show that the variation of the structural unit in tellurite glasses is due to the charge transfer from modifier atoms to TeO6 octahedra with use of first-principles molecular orbital calculations. Orbital overlap population analysis reveals that the transferred electrons to the Te- O antibonding orbital cause breaking Te-O bonds and lead to reducing the coordination number of the Te atom.

Glasses are amorphous solids that exhibit an intricate structural relaxation. A broad relaxation time spectrum always emerges when these systems are perturbed. By using a Langevin-type differential equation to describe the structure dynamicsof these materials, it is depicted how the broad relaxation time spectrum arises due to the stochastic noise and how this affects the system's structure evolution as it is cooled down into the glass transition region. This stochastic model provides a macroscopic as well a microscopic view of the glass relaxation process.

Brillouin light has been used to measure the complex mechanical modulus of the molecular scale structure in oxide melts. The storage modulus reflects the degree of networking and structural integrity, while the loss modulus, which can be attributed to aperiodic motions of structural components, provides a measure of the mobility of these entities. rom the loss modulus it is possible to derive the zero-shear rate viscosity, which is characteristic of a structure in thermodynamic equilibrium, and thereby provide a less encumbered insight into the molecular scale mechanisms that are underlying to the viscous momentum transport.

In this paper we compare the visco-elastic behavior of alkali borates and alkali tellurites, particularly in the temperature range between Tg and the equilibrium melting point. While in borates several mechanisms can be identified as contributing to structural relaxation, in tellurites a single mechanism dominates. The assumption of thermo-rheological simplicity, however, is invalid, and a new visco-elastic model has been developed for the description of our results.

We have performed a study on low frequency modes in several alkali silicate glasses by Raman spectroscopy. The Boson peak region is analyzed with a single parameter ω0 which is believed to characerize the density of states of the system. Analysis of the dependence of ω0 on the nature and concentration of the alkali suggests that the position of the Boson peak is essentially governed by the ratio “force constant” over “mass” of localized oscillator modes. At lower frequency (below 30 cm−1), the “excess” intensity can be explained by considering secondorder processes of the same vibrational modes, superimposed on other (possibly relaxational) modes.

A novel experimental approach involving the fluorescence nonradiative energy transfer technique is employed to study transport processes in thin polymer films near the glass transition through the measurement of energy transfer efficiency, E. Using a layered thin film sample geometry, values of the small molecule diffusion coefficient, , as low as 8 × 10−16 cm2/sec are measured within diffusion times of 3.5 hours. These studies reveal a significant dependence of both the magnitude and temperature dependence of on diffusant size.

Results from the NIST torsional dilatometer have indicated that after a temperature step from equilibrium, the volume (structure) and mechanical response (physical aging) can evolve at different rates, depending on the temperature history. The torsional dilatometer results have been modeled in two ways. First, it was assumed that the volume and mechanical response are governed by different clocks, with the principle of time-aging time superposition employed to evaluate an aging time shift factor atc from the torsional response, which was then compared to a structural shift factor aδ calculated from the evolution of the volume. These results were also investigated using a thermoviscoelastic model based on rational thermodynamics and configurational entropy; this model does not include an explicit assumption of separate time scales, but different time scales for the structure and mechanical properties appear to arise naturally from the formulation. The results from the thermoviscoelastic model show good qualitative agreement with the torsional dilatometer results, although more material data is needed to make an exact comparison.

The viscosities of amorphous and semicrystalline polymeric liquid crystals η have been measured by dynamic mechanical analysis. They have been compared with the rotational correlation times of molecular probes, as drawn by Electron Spin Resonance spectroscopy on two different time scales. In all the cases the correlation times of the spinning motion of a cigar-like probes τ| and η are related by a fractional Debye-Stokes-Einstein law, i.e.η| α ηξ, ξ ≤ 1.

We investigate the growth of quenched Xe films formed by deposition onto a cold (15-35K) substrate via in situ measurements of x-ray reflectivity and diffraction. Surface roughness, film density, and crystallinity are determined as a function of Xe film thickness, substrate temperature and Xe flux in order to test for dynamic scaling behavior. Deposition of polycrystalline films with random crystallite orientations is achieved through heating of a grafoil sheet that is enclosed in the sample cell and has previously been covered with bulk Xe. At 16K the films are sufficiently quenched to be stable over several days, while at 25K annealing takes place. Differing atomic mobilities at different temperatures lead to contrasting scaling behavior. The substrate remains unchanged under repeated film deposition and desorption and therefore allows a systematic comparison of different films.

Molecular dynamics simulations on the solid-liquid transition of copper crystals have been performed. The configulation and the motion of atoms are monitored by RDF. It is seen that the height of the first peak in the RDF, which located at the nearest neighbour distance, decreased drastically as the temperature is increased.

The behavior of electron and phonon excitations in systems with irregular boundaries is discussed on the specific example of prefractal shapes. We show that both electron states and acoustical phonons exhibit localization properties. This effect is stronger when the fractality of the shape is increased. In consequence the electron-phonon interaction in small crystallites should be strongly dependent on their shape or roughness. This localization could play a role in the thermal properties of glasses where internal partial crytallization has no reason to build pseudo-crytalline entities which should be smooth.

Recently a number of experimental studies focusing on the scaling properties of surfaces eroded by ion bombardment provided apparently contradictory results. A number of experiments report the observation of self-affine fractal surfaces, while others provide evidence about the development of a non-fractal periodic ripple structure. To explain these discrepancies, here we derive a stochastic nonlinear equation that describes the evolution and scaling properties of surfaces eroded by ion bombardment. The coefficients appearing in the equation can be calculated explicitly in terms of the physical parameters characterizing the sputtering process. We find that transitions may take place between various scaling behaviors when experimental parameters, such as the angle of incidence of the incoming ions or their average penetration depth, are varied.

Topological disorder places constraints on the local flow of currents in granular thin films of metals and semiconductors. These constraints in turn influence measurable transport properties such as conductance and conductance fluctuations for these films. We quantify disorder in the disposition of grains within real and simulated thin films by applying methods originally developed studying foam evolution. For simulated Voronoi resistor networks the overall conductance of a film with a given grain density achieves a minimum value for an intermediate degree of disorder. Films of equal conductances on either side of this minimum can have strikingly different current distributions. Short range inhomogeneities in the size and placement of grains lead to large scale conductivity inhomogeneities in disordered films. This renders the disordered films more susceptible to 1/f noise for systems with nonlinear intergrain coupling due to factors such as hydrogen diffusion. We discuss the results of simulations of such systems in the context of transport and scanning probe microscopy measurements on a-Si:H thin films.