Ab initio total energy calculations using the plane-wave pseudopotential method based on density functional theory were carried out to investigate the structural, energetic and electronic properties of A2Ti2O7 (A = La, Gd and Yb) pyrochlores. It turned out that the formation energies of antisite defects are not linearly dependent on the ratio of the cation radii, and, for the three compositions...

Ice VIII is a high-density form of H2O that amorphizes upon heating after being decompressed to 0 kbar. Here we investigate by first principles the structural and vibrational properties of ice VIII under decompression. We have reproduced the peculiar nonlinear behavior of some stretching and translational modes under decompression and relate this behavior to the eminent collapse of the hydrogen...

Damage build up and amorphization in Si, induced by 25 keV Si 5 cluster ions and similar mass Cs ions have been studied using transmission electron microscopy and channeling Rutherford back-scattering spectrometry. The threshold dose for amorphisation is found to be just below ∼ 15 eV/atom with saturation occurring above 17 eV/atom. Amorphisation is seen to be a nucleation and growth process wi...

The paper reviews the results of experimental studies and thermodynamical modelling of metastable T –P diagrams of initially amorphous GaSb–Ge and Zn–Sb alloys which provide a new insight into the problem of pressure-induced amorphization.

The structure evolution and crystallization processes of Sb2Te-TiO2 films have been investigated. The Sb2Te-rich nanocrystals, surrounded by TiO2 amorphous phases, are observed in the annealed Sb2Te-TiO2 composite films. The segregated domains exhibit obvious chalcogenide/TiOx interfaces, which elevate crystallization temperature, impede the grain growth and increase crystalline resistance. Com...

Large-scale molecular dynamics simulations of nanoindentation on a (100) oriented silicon surface were performed to investigate the mechanical behavior and phase transformation of single crystalline silicon. The direct crystalline-to-amorphous transformation is observed during the nanoindentation with a spherical indenter as long as the applied indentation strain or load is large enough. This a...

Present-day multimedia strongly rely on rewritable phase-change optical memories. We demonstrate that, different from the current consensus, Ge(2)Sb(2)Te(5), the material of choice in DVD-RAM, does not possess the rocksalt structure but more likely consists of well-defined rigid building blocks that are randomly oriented in space consistent with cubic symmetry. Laser-induced amorphization resul...

Hybrid glasses connect the emerging field of metal-organic frameworks (MOFs) with the glass formation, amorphization and melting processes of these chemically versatile systems. Though inorganic zeolites collapse around the glass transition and melt at higher temperatures, the relationship between amorphization and melting has so far not been investigated. Here we show how heating MOFs of zeoli...

Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in ...

Site restoration activities at DOE facilities and the permanent disposal of nuclear waste inevitably involve understanding the behavior of materials in a radiation field. Radionuclide decay and the associated radiation fields lead to physical and chemical changes that can degrade or enhance important material properties. Alpha-decay of the actinide elements and beta-decay of the fission product...