We demonstrate how by taking better account of electron correlations in the $3d$ shell metal ions nickel oxide it is possible to improve description both energy loss spectra and parameters characterizing structural stability material compared with local spin density functional theory.

Finnis–Sinclair potentials are developed for computer simulations in which van der Waals type interactions between well separated atomic clusters as important the description of metallic bonding at short range. The always favour f.c.c. and h.c.p. structures over b.c.c. structure. They display convenient scaling properties both length energy, a number perfect crystal may be derived analytically.

An atomistic study of tilt grain boundary structures in f.c.c. metals has been made. The principal aim this is to understand the structure long-period (‘general’) boundaries. Boundaries for which Σ< 491 were considered, where Σ reciprocal density coincidence sites. work presented three parts. In paper series studies symmetrical boundaries aluminium and copper are reported. One main objectives determine whether stress fields localized dislocations exist deviated far from any short-period...

Abstract The influence of Mott-Hubbard electron-electron correlations on the electronic structure and structural stability uranium dioxide (UO2) has been analysed using local spin-density approximation (LSDA) + U approach. We have found that inclusion a term describing Hubbard on-site repulsion between 5f electrons results in dramatic improvement description equilibrium magnetic UO2 for which conventional LSDA calculations incorrectly predict non-magnetic metallic ground state. presence band...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation J. B. Pethica, A. P. Sutton; On the stability of a tip flat at very small separations. Journal Vacuum Science Technology A 1 July 1988; 6 (4): 2490–2494. https://doi.org/10.1116/1.575577 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar...

We compare experimentally observed electron energy loss spectra (EELS) of uranium dioxide UO2 and nickel monoxide NiO with the results ab-initio calculations carried out by using a method combining local spin density approximation Hubbard U term (the LSDA + method). show that taking better account strong Coulomb correlations between electrons in 5f shell ions 3d it is possible to arrive at description spectra, cohesive energies elastic constants both oxides compared functional theory. For we...

Abstract High-resolution electron microscopy experiments have been performed to explore the bcc—9R transformation and subsequent elastic relaxation of Cu precipitates in an Fe—Cu alloy aged at 550°C. It was found that both irradiation (at energy 400 kV) thermal annealing caused rotation close-packed (009)9R planes twinned 9R precipitates. For kV irradiation, such rotations were observed smaller than about 12nm diameter. specimens cooled from ageing temperature 550°C a given up −60°C, then...

The results of the study symmetrical tilt boundaries, reported in preceding part I, are generalized to asymmetrical boundaries. A classification boundaries cubic crystals is developed that reveals which choose order equilibrium faceting or intrinsic grain boundary dislocations (g.b.ds) accommodating a misorientation. Two series atomistic studies structures presented based on this classification. first long-period (27 ^ 97) [110] aluminium. aims investigate whether these composed fundamental...

Large scale molecular simulations to model the formation of polyamide membranes have been carried out using a procedure that mimics experimental interfacial polymerization trimesoyl chloride (TMC) and metaphenylene diamine (MPD) monomers. A coarse-grained representation monomers has developed facilitate these simulations, which captures essential features stereochemistry amide bonding between them. Atomic models are recreated from final representations. Consistent with earlier treatments,...

The local spin-density approximation+$U$ method has been applied to identify the origin of surface electronic states on (100) nickel monoxide. results ab initio calculations show a substantial reduction forbidden gap at and point presence two types associated with termination crystal lattice. energy one corresponds top valence band wave function this state is predominantly localized oxygen sites. other situated bottom conduction its these explains contrast reversal scanning tunneling...

Recent experiments suggest that gold single-atom contacts and atomic chains break at applied voltages of 1 to 2 V. In order understand why current flow affects these defect-free conductors, we have calculated the current-induced forces on atoms in a Au chain between two electrodes. These are not by themselves sufficient rupture chain. However, reduces work chain, which results dramatic increase probability thermally activated spontaneous fracture This embrittlement poses fundamental limit...

The authors' develop a general formulation of the problem elastic transport between two semi-infinite systems, connected by system finite size, and derive expressions for current in differential conductance such circuit limit zero interactions carriers. These are exact applied voltage, coupling components circuit, temperature circuit. They then apply their results tight-binding approximation to three specific cases: one-atom contact, finite, disordered one-dimensional chain, generalized...

The results of atomistic calculations long-period tilt boundaries, which were reported in the preceding parts I and II, are generalized represented concisely by using two-dimensional lattices, called decomposition lattices. basis vectors a lattice characterize two fundamental structural elements composing all boundaries continuous series boundary structures. Conversely, governing condition on is that structure can change continuously throughout misorientation range between vectors. On...

This article examines the time to activate Frank–Read sources in response macroscopic strain rates ranging from 101 s−1 1010 aluminium under athermal conditions. We develop analytical models of bowing a pinned dislocation segment as well numerical simulations three dimensional dynamics. find that rate has direct influence on both activation and source strength at up 106 s−1, increases almost proportion rate. contributes increase yield stress materials these rates. Above speed segments...

When a metal is subjected to extremely rapid compression, shock wave launched that generates dislocations as it propagates. The evolves into characteristic two-wave structure, with an elastic preceding plastic front. It has been known for more than six decades the amplitude of decays farther travels metal: this "the decay precursor." precursor dynamic yield point because marks transition from behavior. In Letter we provide full explanation attenuation using first method dislocation dynamics...

The technological importance of polycrystalline strontium titanate $({\text{SrTiO}}_{3})$ is directly linked to its interfacial and grain boundary properties, which are at present poorly understood. A complete understanding (including links with experiment) requires information from many length scales, including electronic atomistic, up microstructural macroscopic. In addition, the size complexity general boundaries makes first-principles simulations prohibitively expensive. We have tested...

Isolated kinks on thermally fluctuating (1/2)<111> screw, <100> edge and dislocations in bcc iron are simulated under zero stress conditions using molecular dynamics (MD). Kinks seen to perform stochastic motion a potential landscape that depends the dislocation character geometry, their provides fresh insight into coupling of heat bath. The kink formation energy, migration barrier friction parameter deduced from simulations. A discrete Frenkel-Kontorova-Langevin (FKL) model is able...

In this article, it is demonstrated that current methods of modelling plasticity as the collective motion discrete dislocations, such two-dimensional dislocation (DDP), are unsuitable for simulation very high strain rate processes (10 6 s −1 or more) plastic relaxation during shock loading. Current DDP models treat dislocations quasi-statically, ignoring time-dependent nature elastic fields dislocations. It shown assumption introduces unphysical artefacts into system when simulating...

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence and their emergence film create valleys composed dissociated edge dislocations ridges where partial have recombined. Geometric analysis simulations indicated that were created by an out-of-plane rotation driven reduction boundary energy. These results suggest in general, it is impossible form flat two-dimensional films other metals...

Abstract A method of optimizing the thermally averaged structure a defect in crystal at finite temperature is presented. The basic idea to augment interatomic forces that apply OK with temperature-dependent contributions arise from minimization free energy temperature. and thermodynamic properties can then be obtained molecular statics program. expressed within harmonic approximation, but since potential O K anharmonic, there an additional force arising vibrational energy. same term gives...