The response of titanate pyrochlores (A2Ti2O7, A = Y, Gd and Sm) to electronic excitation is investigated utilizing an ab initio molecular dynamics method. All the titanate pyrochlores are found to undergo a crystalline-to-amorphous structural transition under a low concentration of electronic excitations. The transition temperature at which structural amorphization starts to occur depends on t...

We demonstrate that there is no ideal glass transition in a binary hard-disk mixture by explicitly constructing an exponential number of jammed packings with densities spanning the spectrum from the accepted amorphous glassy state to the phase-separated crystal. Thus the configurational entropy cannot be zero for an ideal amorphous glass, presumed distinct from the crystal in numerous theoretic...

objectives: the aim of this study was to evaluate and compare the retentive strength of orthodontic bands cemented with amorphous calcium phosphate (acp)-containing and conventional glass ionomer cements (gics). materials and methods: one-hundred-and-twenty mandibular third molars were embedded in acrylic resin blocks with the buccal surface of crowns perpendicular to the base of the mold. the ...

We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40 K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation. We find that the decrease in internal surface ...

By means of a finite elements technique we solve numerically the dynamics of an amorphous solid under deformation in the quasistatic driving limit. We study the noise statistics of the stress-strain signal in the steady-state plastic flow, focusing on systems with low internal dissipation. We analyze the distributions of avalanche sizes and durations and the density of shear transformations whe...

The reflection-absorption infrared (RAIRS) spectra of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]Tf(2)N) are presented for liquid as well as for amorphous and crystalline solid films. The liquid and amorphous films show rather similar spectra, indicating that the film structure is similar in both cases. On the other hand, these spectra differ considerably from those of...

In this paper, we propose two structural models of amorphous GaN at different densities, obtained from approximate ab initio molecular dynamics. The network models we obtain are highly disordered but exhibit a large state-free optical gap, and have no homopolar bonds (or odd-membered rings). The radial distribution function, local bonding, and electronic density of states are described. We find...

Proteins are known to undergo a dynamical transition at around 200 K but the underlying mechanism, physical origin, and relationship to water are controversial. Here we report an observation of a protein dynamical transition as low as 110 K. This unexpected protein dynamical transition precisely correlated with the cryogenic phase transition of water from a high-density amorphous to a low-densi...

We study a polydisperse soft-spheres model for colloids by means of microcanonical Monte Carlo simulations. We consider a polydispersity as high as 24%. Although solidification occurs, neither a crystal nor an amorphous state are thermodynamically stable. A finite size scaling analysis reveals that in the thermodynamic limit: (a) the fluid-solid transition is rather a crystal-amorphous phase-se...