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...

Showed that the calculated activation energy for • AlH3 vacancy diffusion in NaAlH4 is 85 kJ/mol H2, suggesting that it is the rate-limiting step in hydrogen release kinetics from Ti-doped samples. Obtained the activation energies for surface• controlled vacancy creation in pure undoped NaAlH4, showed that vacancy creation limits the dehydrogenation kinetics for particle sizes above ~0.1 μm. Id...

The formation of extended defects in graphene from the coalescence of individual mobile vacancies can significantly alter its mechanical, electrical and chemical properties. We present the results of ab initio simulations which demonstrate that the strain created by multi-vacancy complexes in graphene determine their overall growth morphology when formed from the coalescence of individual mobil...

We present a theoretical study of the interaction of vacancies with a tilt grain boundary in aluminum based on the density functional theory. The grain boundary volume expansion and vacancy induced contraction are calculated and compared for the nearest-neighbor atoms, and the former is found to be smaller than the latter. The formation energy of a vacancy placed at various layers in the grain ...

Formation of metal rich conductive filaments and their rearrangements determine the switching characteristics in HfO2 based resistive random access memory (RRAM) devices. The initiation of a filament formation process may occur either via aggregation of pre-existing vacancies randomly distributed in the oxide or via generation of new oxygen vacancies close to the pre-existing ones. We evaluate ...

Cuprous oxide (Cu2O) is an attractive material for solar energy applications, but its photoconductivity is limited by minority carrier recombination caused by native defect trap states. We examine the creation of trap states by cation vacancies, using first principles calculations based on density functional theory (DFT) to analyze the electronic structure and calculate formation energies. With...

We report first-principles total-energy density-functional theory electronic structure calculations for the neutral and charge states of H intrinsic ~Frenkel pair! and extrinsic ~H vacancy or interstitial! point defects in KH2PO4. The relaxed atomic structures, the formation energy, the ionization energy, and electron and hole affinities for the various defects have been calculated. For the Fre...