Proteins are complex systems that share essential properties with viscous liquids and polymers. Structure, dynamics, and function of proteins are strongly interrelated, and structural and dynamic aspects can be revealed by studying protein function. Here we report measurements of the kinetics of intramolecular electron transfer (ET) from the primary quinone (QA) to the special pair (P) of reaction center (RC) proteins from Rhodobacter sphaeroides as a function of temperature (5 to 300 K) and illumination protocol (cooled in the dark and under illumination from 280 K). From the data, information about structural heterogeneity, relaxations and fluctuations of these molecules is obtained.

The structure, the energy landscape, and the dynamics of proteins and glasses are similar. Both types of systems display characteristic nonexponential time dependencies of relaxation phenomena. Experiments suggest that both, proteins and glasses, are heterogeneous and that this fact causes the observed time dependence. This result is discussed in terms of the rough energy landscape characteristic of complex systems.

We obtain valuable information about medium-range order in amorphous semiconductors from variable coherence microscopy, a new quantitative approach to TEM. The technique reveals three-body and higher-order atomic correlation functions, which are sensitive to medium-range order. Preliminary experimental evidence for structural changes on annealing has been found for amorphous semiconductor films, with pronounced medium-range order seen only in unannealed films.

Network structures of several kinds of oxide glasses were analyzed by means of neutron or x-ray diffraction method and molecular dynamics (MD) simulations including silicate, borate and tellurite glasses. The basic scheme of the structure highly depends on the bonding nature of network forming oxide, but the size of the alkali ions is another important factor to control the network structure of the glass. Structures of silicate glasses are rather easily reproduced by means of MD simulation, whereas borate or tellurite glass structures are hard to be constructed by MD calculation with only 2-body potentials. It is necessary to use adequate potentials to control the bonding angles of O-M-O or M-O-M. The network structure of tellurite glass seems very complex because of the shape of structural units with low symmetry, the use of a new kind of potential was found indispensable to reproduce the glass structure by MD.

In addition to the network structure, the polarization of ions seems to be important to understand the whole vision of oxide glass structures. A new kind of MD was developed which took polarization of ions into account to understand the mixed alkali effects in silicate glasses.

The viscosities of the Zr46.75Ti8.25Cu7.5Ni10Be27.5 and the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass forming liquids was determined from the melting point down to the glass transition in the entire temperature range of the supercooled liquid. The temperature dependence of the viscosity in the supercooled liquid obeys the Vogel-Fulcher-Tammann (VFT) relation. The fragility index D is about 20 for both alloys and the ratio between glass transition temperature and VFT temperature is found to be 1.5. A comparison with other glass forming systems shows that these bulk metallic glass formers are strong liquids comparable to sodium silicate glass. Furthermore, they are the strongest among metallic glass forming liquids. This behavior is a main contributing factor to the glass forming ability since it implicates a higher viscosity from the melting point down to the glass transition compared to other metallic liquids. Thus, the kinetics in the supercooled liquid is sluggish and yields a low critical cooling rate for glass formation. The relaxation behavior in the glass transition region of the alloys is consistent with their strong glassy nature as reflected by a stretching exponent that is close to 0.8. The microscopic origin of the strong liquid behavior of bulk metallic glass formers is discussed.

During a recent study of supercooled liquids in the system Y2O3-Al2O3, a first-order phase transition between two liquid phases with the same composition, but different structure and density, was observed to occur. The transition occurred close to the glass transformation of the two liquids, so that both phases were quenched to metastably coexisting glasses. We report further studies on the liquids and glasses in this system, prepared by rapid (roller) quenching and by containerless levitation techniques.

Borate glasses are an enigma in that there is now increasing evidence that their structures are dominated by superstructural units, which comprise well defined arrangements of the basic BO3 and BO4 structural units, with no internal degrees of freedom in the form of variable bond or torsion angles. In the present paper, it is shown that considerable insight into the structure of borate glasses can be gained from a study of the corresponding crystalline polymorphs. A simple, model is proposed to predict the fraction, x4, of 4-fold co-ordinated boron atoms in vitreous borate networks and the topological criteria for the formation of such networks are discussed, taking into account the degrees of freedom necessary for conventional glass formation.

A direct connection between the local topology of the atomic structure of liquids and glasses and thermodynamic quantities through the atomic level stresses is suggested for metallic alloys. In particular the role of local topological instability in the phase transformations involving liquid and glass will be discussed. It is pointed out that a single local geometrical criterion can explain various phase transformations, such as melting, glass transition, and glass formation by solid state reaction and liquid quenching.

Information about the spatial distribution of sodium cations in sodium tellurite glasses is obtained from the decay rate of sodium spin echoes. The spin echoes decay due to the magnetic dipole coupling between sodium nuclei, with each pair contributing to the rate in proportion to 1/r6, where r is the distance between the pair. The experiment is used to probe the sodium distributions in sodium tellurite glasses as a function of sodium oxide content, and the resulting distance distributions are interpreted by comparison with model distributions. At low sodium contents the distribution is similar to that of a random model in which the sodium ions are constrained to be no closer than a minimum cut-off distance. At higher contents the distributions deviate significantly from the random model, suggesting the onset of medium range order in the distribution of sodium ions. This order is most pronounced at 20% sodium oxide content, the composition at which this glass has been claimed to have maximum stability against devitrification.

A simple macroscopic thermodynamic model for first order transitions between two amorphous phases in a one component liquid is reviewed, augmented and evaluated. The model presumes the existence in the liquid of two species, whose concentrations are temperature and pressure dependent and which form a solution with large, positive deviations from ideality. Application of the model to recent data indicates that water can undergo an amorphous/amorphous phase transition below a critical temperature Tc of 217K and above a critical pressure Pc of 380 atm.

Benzophenone supercools to a glass when cooled to −100°C. In fact, it is difficult to freeze benzophenone on cooling. In this investigation, the effect of cooling rate and the minimum cooling rate to obtain benzophenone as a glass is determined. From the glassy state, the influence of heating rate on the solidification temperature of benzophenone is determined. When heated at 3°C/min., solidification starts at about −29°C. Upon additional heating, melting usually starts at about +24°C, which is 23°C lower than the solid equilibrium structure melting temperature of 47°C. Occasionally the solid that forms at about −29°C undergoes a solid state phase transformation at about +22°C, when heated at 3°C/min. If this solid state phase transformation occurs, then the solid benzophenone starts to melt at 47°C. When solid benzophenone with the equilibrium structure is cooled to −100°C, no solid state phase transformation occurs. It appears that the structure that solidifies at −29°C is metastable.

We have performed neutron scattering experiments on rare-earth (La, Pr, Ho) doped phosphate glasses around the metaphosphate composition R(PO3)3. Combining the diffraction experiment with Reverse Monte Carlo simulations we obtain a 3-D model of the structure. Our models propose a rare-earth ion environment primarily consisting of oxygens with the average rare earth-oxygen distances; 2.56, 2.51 and 2.40 Å for the La, Pr and Ho samples respectively. We also observe that the rare earth ions are not uniformly distributed. The first R-R shell is on avergae about 3.3 Å to be compared with a value of 7 Å for a uniform distribution of R ions in the structure. From the models we also conclude that a chain like structure of the phosphate network is in agreement with the experiment.

We consider 2D lattices which are disordered by an external field, in this case by a dense, random distribution of attractive pinning centers of an underlying substrate. The preferred configuration of the 2D system with screened-Coulomb two-body interactions and a fixed number of particles is a triangular lattice configuration. The pinning centers strongly affect the triangular lattice configuration. By keeping the location and the density of the pinning centers fixed, we study the effects of pinning strength on the structural properties of the lattice. We find that the strongly disordered lattice prefers to form irregular domains of size s which are composed entirely of topological defects. The distribution of sizes of these domains, D(s) suggest that s−τ for sufficiently large s. Our results are consistent with τ ≥ 2 in the solid phase and τ < 2 in the liquid phase. We present a general argument in support of our findings and suggest that the physics which dictates the structure of 2D lattices on substrates with randomly distributed pinning centers is the same as that for a broad range of problems in which an external field strongly influences the behavior of an interacting physical system.

We present a molecular dynamics simulation study of the liquid-solid transition in a two dimensional system consisting of particles of two different sizes interacting via a truncated Lennard-Jones potential. We work with equal number of particles of each kind and the dispersity Δ in the sizes of the particles is varied by changing the ratio of the particle sizes only. For the monodisperse case (Δ = 0) and for small values of Δ, we find a first order liquid-solid transition on increasing the volume fraction p of the particles. As we increase Δ, the first-order transition coexistence region weakens gradually and completely disappears at high dispersities around Δ = 0.10. At these values of dispersity the high density phase lacks long range translational order but possesses orientational order with a large but finite correlation length. The consequences of this effect of dispersity on the glass transition and on the melting transition in general are discussed.

We report a new experimental approach to study the glass transition and glassy dynamics on a mesoscopic scale. Non contact atomic force microscopy is employed to measure dielectric fluctuations of glass forming polymers such as PVAc. Force modulation techniques, performed with the same instrument, allow us to study viscoelastic properties. A custom-built variable temperature UHV AFM with exceptional thermal stability utilizing piezoresistive cantilevers was used. First results on PVAc include large fluctuations of the viscoelastic properties as a function of applied stress below the glass transition.

The existence of liquid-liquid miscibility gap in ferric ferrous oxide-silica system has been reported, however, the phase separation phenomena and the derived morphology of the phase separated glasses are uncertain. In this study, the melt-quenched samples of 5 Fe3O4-95 SiO2 and 15 Fe3O4-85 SiO2 (mol%) were prepared by melting at 2300°C or 2200°C (expected to be above miscibility gap), and subsequently at 1800°C or 1750°C (in immiscible region) by use of infrared image furnace and quenching at the rate of ≈102 K/sec. The glassy materials exhibited phase separation having discrete spherical particles or interconnected structure due to the composition, melting temperature and time. Also, the segregation of Fe component occurred during melting, which was caused by the difference of specific gravity of components in the melt.

The effect of iron and oxygen additions on the thermal stability of rapidly quenched amorphous Zr65Al7.5Cu17.5Ni10) was studied by x-ray diffraction and differential scanning calorimetry. With increasing Fe content the glass transition temperature Tg and the crystallization temperature Tx shift to higher temperatures. The increase is more significant for Tg than for Tx, resulting in a decrease of the supercooled liquid region with increasing Fe content. For oxygen additions Tx decreases with increasing oxygen content whereas Tg increases slightly, causing a decrease of the supercooled liquid region with increasing oxygen content. The results reveal that even minor iron or oxygen contaminations lead to drastic changes in the glass transition behavior and the crystallization mode. Large iron or oxygen contents lead to the formation of nanocrystalline microstructures instead of coarse-grained material.

Spectroscopie properties of selected 4f-elements in a sol-gel and two high temperature silicate based glasses are reported. In particular, the spectral properties of the Eu3+ ion have been used to probe the local coordination environment of the f-elements in these glass matrices. Luminescence studies of the high temperature glasses indicated that the electric dipole allowed f-f transitions dominate the spectra which suggests that the local symmetry around the 4f-ions is low. Temperature-dependent spectroscopie studies of the sol-gel glasses indicated that the f-elements retain a “solution-like” environment prior to thermal processing. After heat treatment, an increase in the emission intensities of the electric-dipole transitions is accompanied by a concomitant decrease in the magnetic-dipole allowed transitions. Moreover, excited state interactions has also been observed in the high temperature glasses that contain certain multiple f-elements. In Pr-Sm systems, exclusive excitation of the Sm3+ ion with a 514 nm argon ion laser line provides a higher-energy emission band (ca. 490 nm) from the Pr3+ ion (3P0 → 3H4) transition. This energy up-conversion is attributed to energy transfer from the 6H13/2 level of the Sm3+ ion to the 3Hg6 state of the Pr3+ ion. Following a second photon absorption, the Pr3+ ion is excited to the emitting 3P0level.

Borovanadate glasses with mixed conductivity, i.e., simultaneous ionic and electronic carriers have been obtained in the system (100−x)[B2O3-Li2O]-xV2O5 (0 ≤ x ≤ 30 mole%). To understand the origin of the conductivity in these glasses, the compositional dependence of the network structure has been studied by Raman and infrared spectroscopy.

In this work, we report the first spectroscopie observation of octahedrally coordinated pentavalent chromium ions in BaCaMg aluminate glasses. A broad band emission peaking at 780 nm with band width of 3000 cm−1 has been observed at 12K. The measurements of fluorescence decay, time-resolved emission and excitation spectra reveal that the emission band is an overlapped luminescence originating from both the 2E to 2T2 transition of octahedrally coordinated Cr5+ and a charge transfer transition of Cr6+O4 groups.