نتایج جستجو برای: vacancy
تعداد نتایج: 7609 فیلتر نتایج به سال:
The energy required to form and remove vacancies on metal surfaces mediates the rate of mass transport during a wide range of processes. These energies are known to be sensitive to environmental conditions. Here, we use electronic structure density functional theory calculations to show that the surface vacancy formation energy of silver changes markedly in the presence of adsorbed and dissolve...
The earlier-suggested generalized Gibbs distribution approach to the configurational kinetics of non-equilibrium alloys is extended to the case of many-component alloys and the realistic vacancy-mediated atomic exchange mechanism is incorporated. Exact and approximate equations for the temporal evolution of atomic distributions as well as for the free energy of a non-equilibrium alloy are prese...
We have identified stable fourfold coordinated vacancy clusters Vn 3 n 18 in Si using a combination of metropolis Monte Carlo, tight-binding molecular-dynamics, and density-functional theory calculations. Our calculations show that the small vacancy defects exclusively favor fourfold coordination thermodynamically rather than hexagonal ringlike structure formation, which has widely been adapted...
Motivated by the idea of impurity band superconductivity in heavily Boron doped diamond, we investigate the doping of various elements into diamond to address the question, which impurity band can offer a better DOS at the Fermi level. Surprisingly, we find that the vacancy does the best job in producing the largest DOS at the Fermi surface. To investigate the effect of disorder in Anderson l...
Electrical properties of semiconductor materials are greatly influenced by point defects such as vacancies and interstitials. These defects are common and form during the growth and processing of the material. Positron annihilation spectroscopy is a method suitable for detecting and studying vacancy-type lattice defects. In this work, the formation, properties, and annealing of vacancy defects ...
We have computed the variation of the vacancy formation energy with pressure for Ta. Total energy calculations were performed for 16 and 54 atom supercells using a mixed basis pseudopotential method which uses pseudoatomic orbitals and low energy plane waves as the basis set, within density functional theory (LDA and GGA). The vacancy formation energy is found to increase from 2.95 eV at ambien...
Recent experiments indicate that proton irradiation triggers ferromagnetism in originally nonmagnetic graphite samples while He ion bombardment has a much smaller effect. To understand the origin of irradiation-induced magnetism, we have performed spin-polarized density functional theory calculations of the magnetic properties of the defects which are most likely to appear under irradiation vac...
We demonstrate a novel pathway to control and stabilize oxygen vacancies in complex transition-metal oxide thin films. Using atomic layer-by-layer pulsed laser deposition (PLD) from two separate targets, we synthesize high-quality single-crystalline CaMnO3 films with systematically varying oxygen vacancy defect formation energies as controlled by coherent tensile strain. The systematic increase...
A numerical model to estimate critical times required for nanovoid nucleation in high-purity aluminum single crystals subjected to shock loading is presented. We regard a nanovoid to be nucleated when it attains a size sufficient for subsequent growth by dislocation-mediated plasticity. Nucleation is assumed to proceed by means of diffusion-mediated vacancy aggregation and subsequent vacancy cl...
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