The structure of amorphous silicon in its pure and hydrogenated form has attracted wide interest over the last five decades. This substantial interest is twofold. Firstly, amorphous silicon is a technologically highly significant material with many applications such as photovoltaic cells or thin-film transistors. Secondly, physically it is a fundamentally interesting material which has been reg...

Crystallization of solid is generally slow in kinetics for atoms trapped in solids. Phase-change materials (PCMs) challenge current theory on its ultrafast reversible amorphous-to-crystal transition. Here by using the stochastic surface walking global optimization method, we establish the first global potential energy surface (PES) for Ge2Sb2Te5. By analyzing all structures on the global PES, w...

Co-processing an active pharmaceutical ingredient (API) with a low Tg excipient has been previously reported to be an effective strategy for preventing drug amorphisation on milling. This technique relies on the ability of the excipient to form a molecular dispersion with the amorphous API during the milling process. The presence of the excipient within the amorphous phase induces a reduction o...

Structural transformations between disordered phases, such as liquid-liquid and amorphousamorphous transformations (polyamorphic transformations), have been a focus of interest for the past years. In water, amorphous-amorphous transformation was experimentally observed and transformation between two distinct liquid forms has also been examined [1]. Since a typical atomic configuration of silico...

The question of the local stability of the ~replica-symmetric! amorphous solid state is addressed for a class of systems undergoing a continuous liquid to amorphous-solid phase transition driven by the effect of random constraints. The Hessian matrix, associated with infinitesimal fluctuations around the stationary point corresponding to the amorphous solid state, is obtained. The eigenvalues o...

Preliminary results are reported of the amorphization of Nb-Sn and Nb-Ge alloys by mechanical alloying of the elemental powders. Nb-25 at.% Sn, Nb-25 at.% Ge, and Nb-27 at.% Ge alloys were made amorphous. Differential scanning calorimetry (DSC) indicated a crystallization peak at 995 K for Nb-25 at.% Sn but > 1000 K for the Nb-Ge amorphous alloys. A large endothermic DSC peak and the diffractio...

0022-3093/$ see front matter 2008 Elsevier B.V. A doi:10.1016/j.jnoncrysol.2008.06.106 * Corresponding author. Tel.: +49 40 8998 1861; fa E-mail address: [email protected] (J. Bedna X-ray diffraction experiments indicate that cryomilling of an amorphous CoFeZrB alloy significantly retards mechanically-induced crystallization. After 12 h of milling, the samples consist mostly of an amorpho...

The influence of short-time milling on the atomic structure of amorphous Co(70.3)Fe(4.7)B(25) has been investigated by differential scanning calorimetry (DSC), x-ray powder diffraction (XRD), vibrating sample magnetometer (VSM) and x-ray absorption fine-structure (XAFS) techniques. Our results prove that the milling process crystallizes the initially amorphous sample and that the degree of inhe...

We have modeled the photoinduced volume change in amorphous selenium. After photon absorption, we treated the excited electron and hole independently within the framework of the tight-binding formalism. We found covalent bond breaking in amorphous networks with photoinduced excited electrons, whereas excited holes contribute to the formation of interchain bonds. We also observed a correlated vo...

Methanol oxidation catalysts comprising an outer Pt-shell with an inner Ni-core supported on carbon, (Pt-Ni/C), were prepared with either crystalline or amorphous Ni core structures. Structural comparisons of the two forms of catalyst were made using transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and methanol oxidation activity compar...