Molecular-dynamics (MD) simulations have been carried out on a two-component Lennard-Jones system, quenched into supercooled and amorphous states. Two different regimes of viscous behavior are found in the time window accessible MD simulation studies (of order nanoseconds if units appropriate for argon used). The results dependence self-intermediate scattering function ${\mathit{F}}^{\mathit{s}}$(q,t) show two slow relaxation processes, where slowest (\ensuremath{\alpha} relaxation) can be...

We have revealed, and resolved, an apparent inability of density functional theory, within the local generalized gradient approximations, to describe vacancies in Al accurately consistently. The shortcoming is due electron correlation effects near electronic edges we show how correct for them. find that divacancy energetically unstable anharmonic atomic vibrations explain non-Arrhenius temperature dependence vacancy concentration.

With the purpose to understand fundamental difference between two industrially important classes of hard materials, WC-Co cemented carbides and TiC-Co cermets, we do a comparative study Co/WC Co/TiC interface adhesion. Using first-principles density-functional plane-wave pseudopotential calculations, analyze energetics electronic structure interface, compare with previously reported results for Co/TiC. Values work separation energy are provided set model Co(001)/WC(001) interfaces fcc Co...

In this work, the stability and mobility of protonic defects in acceptor doped $\mathrm{Ba}\mathrm{Zr}{\mathrm{O}}_{3}$ are investigated using density functional theory conjunction with kinetic modeling. The interaction between mobile protons Zr-site substituted trivalent dopants---Ga, Sc, In, Y, Gd---is assessed by extensive mapping migration pathways. all cases, is attractive, which results a stabilization, hence reduction mobility, proton. However, its strength range vary substantially...

We report generalized stacking fault (GSF) curves along the [121] and [110] directions for Pd Al, calculated from first principles. The GSF are applied in classic PN model to calculate Peierls barriers stresses Shockley partials unsplit edge dislocations Al. obtained using relaxed agree well with experiments. numerical results also compared a recently derived analytical expression stress. have been pseudopotential implementation of density functional theory. accuracy method tested by...

We present the results of a detailed molecular-dynamics study relaxation in van der Waals system ortho-terphenyl supercooled regime. The molecule is described by simple rigid three-site model, with interactions between different molecules Lennard-Jones form. find that long-time (\ensuremath{\alpha}) relaxation, as determined from intermediate scattering function, well Kohlrausch law. zero-time amplitude this process, often referred to ``nonergodicity parameter,'' which can be interpreted...

Density functional calculations combined with thermodynamical modeling have been used to investigate defect formation in a perovskite-structured oxide equilibrium an oxygen containing atmosphere. We calculated the electronic structure and energies for anion cation vacancies Ga, Gd, In, Nd, Sc, Y dopants incorporated on different lattice sites ${\mathrm{BaZrO}}_{3}$. On energetic grounds, it is found that most of investigated (with possible exception Nd Gd) preferably substitute Zr atoms...

Density functional calculations have been used to study the electronic structure, preferred sites in lattice, formation energies and vibrational frequencies for hydrogen interstitials different charge states cubic phase of perovskite-structured BaZrO3. By combining ab initio results with thermodynamic modeling, defect at finite temperature pressure has investigated. We demonstrate how site selectivity spatial distribution dopant atoms lattice can be affected by changes environmental...

Density-functional calculations are used to investigate hydrogen diffusion in the solid-state proton conductor $\mathrm{Ba}\mathrm{Zr}{\mathrm{O}}_{3}$. Activation energies and prefactors for rate of transfer reorientation evaluated a defect-free region this simple cubic perovskite-structured oxide. Both semiclassical over-barrier jumps phonon-assisted tunneling transitions between sites considered. It is found that classical barriers elementary steps both order...

The all-inorganic perovskite barium zirconate, BaZrO3, is a widely used material in range of different technological applications. However, fundamental questions surrounding the crystal structure especially regard to its ground-state structure, remain. While diffraction techniques indicate cubic all way down T = 0 K, several first-principles phonon calculation studies based on density functional theory an imaginary (unstable) mode due appearance antiferrodistortive transition associated with...

Abstract Perturbative treatments of the lattice dynamics are widely successful for many crystalline materials; however, their applicability is limited strongly anharmonic systems, metastable crystal structures and liquids. The full these systems can, be accessed via molecular (MD) simulations using correlation functions, which includes dynamical structure factors providing a direct bridge to experiment. To simplify analysis here dynasor package presented as flexible efficient tool that...

Using magnetic particles with sizes in the nanometer range biomedical separation has gained much interest recently due to their higher surface area particle volume and lower sedimentation rates. In this paper, we report our both theoretical experimental investigation of motion a field gradient from 425 nm down 50 nm. measurements, monitor absorbance change sample as concentration varies over time. We also implement Brownian dynamics algorithm investigate influence interactions during compare...

Abstract Segregation energies of oxygen vacancies and protons near three symmetric tilt grain boundaries (GBs) in BaZrO 3 are determined using density functional theory. Two the GBs have [ $ \overline 1 10] direction as axis with a (111) or (112) plane GB plane, while third has [001] (210) plane. Both defects found to segregate all GBs, vacancy segregation –0.5 –1.5 eV proton about –0.8 eV. The effects calculated on defect concentrations electrostatic potential region investigated...

We examine different interface energy relationships at the $\mathrm{WC}(101\ifmmode\bar\else\textasciimacron\fi{}0)$ surface in WC-Co cemented carbide using density-functional theory. To assess stability of WC/WC grain boundaries, $90\ifmmode^\circ\else\textdegree\fi{}$-twist boundaries and a $27\ifmmode^\circ\else\textdegree\fi{}$-twist boundary are considered. In addition, we investigate adhesion properties $\mathrm{Co}(001)/\mathrm{WC}(101\ifmmode\bar\else\textasciimacron\fi{}0)$ by...

We have investigated the likelihood of a high transient mobility for hyperthermal adatoms resulting from dissociative adsorption diatomic molecule, in particular O2 on Al(111), using dynamical simulations model potentials fitted to available first principle data. find no evidence large mobility, compatible with conclusions by Brune et al. [Phys. Rev. Lett. 68, 624 (1992)], O atoms moving chemisorption potential energy surface O/Al(111) system. Our findings are more STM results Pt(111). also...