The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform

Michael J. Demkowicz - One of the best experts on this subject based on the ideXlab platform.

  • The role of thermal spike compactness in radiation-induced disordering and Frenkel Pair production in Ni3Al
    Scripta Materialia, 2012
    Co-Authors: S. A. Skirlo, Michael J. Demkowicz
    Abstract:

    We show that the shape of the kinetic energy distribution in radiation-induced thermal spikes may be described using a dimensionless number, proportional to (volume) 2/3 /(surface area), known as compactness. The disorder produced in thermal spikes in Ni 3 Al increases with compactness because the thermal spike cooling rate, which determines the time available for thermal disordering, decreases with compactness. On the other hand, Frenkel Pair production is inversely correlated to compactness because longer thermal spike lifetimes enhance vacancy–interstitial recombination.

  • The role of thermal spike compactness in radiation-induced disordering and Frenkel Pair production in Ni3Al
    Scripta Materialia, 2012
    Co-Authors: S. A. Skirlo, Michael J. Demkowicz
    Abstract:

    We show that the shape of the kinetic energy distribution in radiation-induced thermal spikes may be described using a dimensionless number, proportional to (volume)[superscript 2/3]/(surface area), known as compactness. The disorder produced in thermal spikes in Ni[subscript 3]Al increases with compactness because the thermal spike cooling rate, which determines the time available for thermal disordering, decreases with compactness. On the other hand, Frenkel Pair production is inversely correlated to compactness because longer thermal spike lifetimes enhance vacancy–interstitial recombination

  • interface structure and radiation damage resistance in cu nb multilayer nanocomposites
    Physical Review Letters, 2008
    Co-Authors: Michael J. Demkowicz, R G Hoagland, J P Hirth
    Abstract:

    We use atomistic simulations to show that upon removal or insertion of atoms, misfit dislocations in Cu-Nb interfaces shift between two adjacent planes, forming Pairs of extended jogs. Different jog combinations give rise to interface structures with unlike densities but nearly degenerate energies, making Cu-Nb interfaces virtually inexhaustible sinks for radiation-induced point defects and catalysts for efficient Frenkel Pair recombination.

M D Mccluskey - One of the best experts on this subject based on the ideXlab platform.

Igor A. Abrikosov - One of the best experts on this subject based on the ideXlab platform.

  • N vacancy, self-interstitial diffusion, and Frenkel-Pair formation/dissociation in TiN studied by \textit{ab-initio} and classical molecular dynamics
    Bulletin of the American Physical Society, 2015
    Co-Authors: Davide Sangiovanni, Bj "{o}rn Alling, Lars Hultman, Igor A. Abrikosov
    Abstract:

    den — We use ab-initio and classical molecular dynamics (AIMD, CMD) to simulate diffusion of N vacancy and N self-interstitial point-defects in B1 TiN. The physical properties of TiN, important material system for thin film and coatings applications, are largely dictated by concentration and mobility of point defects. We determine N dilute-point-defect diffusion pathways, activation energies, attempt frequencies, and diffusion coefficients as a function of temperature. In addition, MD simulations reveal an unanticipated atomistic process, which controls the spontaneous formation of N-self-interstitial/N-vacancy Pairs (Frenkel Pairs) in defect-free TiN. This entails that a N lattice atom leaves its bulk position and bonds to a neighboring N lattice atom. In most cases, Frenkel-Pair N I and N V recombine within a fraction of ns; 50% of these processes result in the exchange of two nitrogen lattice atoms. Occasionally, however, Frenkel-Pair N-interstitial atoms permanently escape from the anion vacancy site, thus producing unPaired N I and N V point defects.

  • n vacancy self interstitial diffusion and Frenkel Pair formation dissociation in tin studied by textit ab initio and classical molecular dynamics
    Bulletin of the American Physical Society, 2015
    Co-Authors: Davide Sangiovanni, Bj "{o}rn Alling, Lars Hultman, Igor A. Abrikosov
    Abstract:

    den — We use ab-initio and classical molecular dynamics (AIMD, CMD) to simulate diffusion of N vacancy and N self-interstitial point-defects in B1 TiN. The physical properties of TiN, important material system for thin film and coatings applications, are largely dictated by concentration and mobility of point defects. We determine N dilute-point-defect diffusion pathways, activation energies, attempt frequencies, and diffusion coefficients as a function of temperature. In addition, MD simulations reveal an unanticipated atomistic process, which controls the spontaneous formation of N-self-interstitial/N-vacancy Pairs (Frenkel Pairs) in defect-free TiN. This entails that a N lattice atom leaves its bulk position and bonds to a neighboring N lattice atom. In most cases, Frenkel-Pair N I and N V recombine within a fraction of ns; 50% of these processes result in the exchange of two nitrogen lattice atoms. Occasionally, however, Frenkel-Pair N-interstitial atoms permanently escape from the anion vacancy site, thus producing unPaired N I and N V point defects.

Michael W. Finnis - One of the best experts on this subject based on the ideXlab platform.

  • Spontaneous Frenkel Pair formation in zirconium carbide
    Physical Review B, 2018
    Co-Authors: Thomas A. Mellan, Andrew Ian Duff, Michael W. Finnis
    Abstract:

    With density functional theory we have performed molecular dynamics simulations of ZrC, which displayed spontaneous carbon Frenkel Pair formation at a temperature of $3200\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, some 500\ifmmode^\circ\else\textdegree\fi{} below the melting point. To understand this behavior, rarely seen in equilibrium simulations, we quenched and examined a set of lattices containing a Frenkel Pair. Five metastable structures were found, and their formation energies and electronic properties were studied. Their thermal generation was found to be facilitated by a reduction of between 0.7 and 1.5 eV in formation energy due to thermal expansion of the lattice. With input from a quasiharmonic description of the defect-free energy of formation, an ideal solution model was used to estimate lower bounds on their concentration as a function of temperature and stoichiometry. At 3000 K (0.81 of the melting temperature) their concentration was estimated to be 1.2% per mole in a stoichiometric crystal, and 0.3% per mole in a crystal with 10% per mole of constitutional vacancies. Their contribution to heat capacity, thermal expansion, and bulk modulus was estimated.

  • Spontaneous Frenkel Pair formation in zirconium carbide
    'American Physical Society (APS)', 2018
    Co-Authors: Thomas A. Mellan, Ai Duff, Michael W. Finnis
    Abstract:

    With density functional theory we have performed molecular dynamics simulations of ZrC which displayed spontaneous Frenkel Pair formation at a temperature of 3200 K, some 500 K below the melting point. To understand this behaviour, rarely seen in equilibrium simulations, we quenched and examined a set of lattices containing a Frenkel Pair. Five metastable structures were found, and their formation energies and electronic properties were studied. Their thermal generation was found to be facilitated by a reduction of between 0.7 and 1.5 eV in formation energy due to thermal expansion of the lattice. With input from a quasi-harmonic description of the defect free energy of formation, an ideal solution model was used to estimate lower bounds on their concentration as a function of temperature and stoichiometry. At 3000 K (0.81 of the melting temperature) their concentration was estimated to be 1.2% per mole in a stoichiometric crystal, and 0.3% per mole in a crystal with 10% per mole of constitutional vacancies. Their contribution to heat capacity, thermal expansion and bulk modulus was estimated

Enamul H Khan - One of the best experts on this subject based on the ideXlab platform.