We have investigated, using first-principles calculations, the energetic stability and structural properties of antisites, vacancies substitutional carbon defects in a boron nitride monolayer. found that incorporation atom substituting for one atom, an N-rich growth condition, or nitrogen B-rich medium, lowers formation energy, as compared to antisites vacancy defects. also verify defects, inducing excess boron, such NB BN, are more stable its reverse atmosphere, i.e. is while BN condition....

Two-dimensional (2D) binary XBi compounds, where X belongs to group III elements (B, Al, Ga, and In), in a buckled honeycomb structure may originate sizable gap Z2 topological insulators (TIs). These are characterized by exhibiting single band inversion at the Γ point as well nontrivial edge states their corresponding nanoribbons. By using first-principles calculations, we demonstrate that hydrogenation of layers leads distinct stable crystal structures, which can preserve insulating...

In this work, ab initio density functional theory calculations were performed in order to study the structural and electronic properties of halogens (X = fluorine, chlorine, bromine or iodine) that deposited on both sides graphene single layers (X-graphene). The adsorption these atoms only one side layer with hydrogen adsorbed other was also considered (H,X-graphene). results indicate F-C bond F-graphene system causes an sp(2) sp(3) transition carbon orbitals, similar effects seem occur...

This work investigates, using first-principles calculations, electronic and structural properties of hydrogen, lithium, sodium, potassium rubidium that are adsorbed, in a regular pattern, on graphene surface. The results for H-graphene (graphane) Li-graphene were compared with previous calculations. present do not support claims the Li–C bond such layer would result an sp2 to sp3 transition carbon orbitals, being more compatible some ionic character covalent lithium acting as electron...

We have investigated the structure, adsorption, electronic states, and charge transfer of small water aggregates on surface a graphene layer using density functional theory. Our calculations were focused adsorbates containing up to five molecules interacting with one both sides perfect freestanding sheet. Different orientations respect sites considered. The results show that adsorption energy molecule is primarily determined by its orientation, although it also strongly dependent implemented...

Aggregation, molecular adsorption, and dissociation of water on the Fe(100) surface were investigated using spin-polarized density functional calculations. The preferential sites for H2O, HO, O, H carefully this surface. Also, H2O into + OH species, further O was examined. charge transfer mechanism during these processes, as well small aggregates at different orientations surface, studied within Bader analysis. coverage dependence adsorption properties examined by comparing results a (2 × 2)...

We present in this work results concerning the application of generalized simulated annealing (GSA) algorithm to LEED search problem. The influence visiting distribution function (defined by so-called q(V) parameter) effectiveness method was investigated structural searches for optimization two ten parameters a theory-theory comparison CdTe(110) system. Results, obtained with scaling relation and probability convergence as number be varied, indicate fast (FSA) (q(V) = 2.0) approach best machine.

First-principles calculations are employed to investigate structural, electronic and topological insulating properties of XBi (X = B, Al, Ga, In) monolayers upon halogenation. It is known that Y-XBi In, Tl; Y F, Cl, Br, I) can originate inversion-asymmetric insulators with large bulk band gaps. Our results suggest Al; may also result in nontrivial phases. Despite the lower atomic number B spin-orbit coupling opens a gap about 400 meV Al), exhibiting an unusual behavior for practical...

The band structure and stability of XBi XBi3 (X = B, Al, Ga, In) single sheets are predicted using first-principles calculations. It is demonstrated that the gap values these new classes two-dimensional (2D) materials depend on both spin-orbit coupling (SOC) type group-III elements in hetero-sheets. Thus, topological properties can be achieved, allowing for viable applications based coherent spin transport at room temperature. effects proved to essential explain tunability by atoms. A clear...

Ionisation distributions of field-ionised ions from liquid metal ion sources are calculated. Various shapes for the emitter region, a range currents and electric field strengths at surface considered. Their effects on energy deficit distribution is presented through numerical calculation gold gallium.

In the last 40 years, low energy electron diffraction (LEED) has proved to be most reliable quantitative technique for surface structural determination. this review, recent developments related theory that gives support LEED determination are discussed under a critical analysis of main theoretical approximation—the muffin-tin calculation. The search methodologies aimed at identifying best matches between and experimental intensity versus voltage curves also considered, with procedures being...

A quantitative structure determination of the $\mathrm{Ag}(111)(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}\mathrm{Sb}$ surface has been performed using low energy electron diffraction. Six possible structural models were tested: Sb overlayers with four different adsorption sites and a substitutional alloy layer, or without stacking fault relative to underlying substrate. The results clearly favor faulted model all outermost layer...

In many field electron emission experiments on single-walled carbon nanotubes (SWCNTs), the SWCNT stands one of two well-separated parallel plane plates, with a macroscopic FM applied between them. For any given location "L" surface, enhancement factor (FEF) is defined as $F_{\rm{L}}$/$F_{\rm{M}}$, where $F_{\rm{L}}$ local at "L". The best measurements from small-radii capped SWCNTs exhibit characteristic FEFs that are constant (i.e., independent $F_{\rm{M}}$). This paper discusses how to...

Magnetic mesoporous particles were synthesized and their magnetic structural properties are reported. The synthesis procedure consists of four steps: (i) preparation magnetite colloidal nanoparticles; (ii) growth a silica layer; (iii) development the structure (iv) template removal. Two different methods for removal studied effectiveness was discussed. Magnetization Mössbauer spectroscopy measurements showed superparamagnetic behavior at room temperature. X-ray diffraction nitrogen...

We investigate, by means of first-principles calculations, the impact a gold surface on proton-transfer guanine–cytosine (GC) DNA base pair. Our calculations employ density functional improvements to correct van der Waals interactions and properly treat weakly bound GC pair at an Au(111) surface. adopted simultaneous double (SDPT) mechanism proposed Löwdin, which may lead spontaneous mutation in structure from specific tautomerization involving pairs. calculated differences energetics...

The electric field in the vicinity of top an emitter with a profile consisting triangular protrusion on infinite line is analytically obtained when this system under external uniform field. same problem also studied features two-stage system, centered rectangular one line. These problems are approached by using Schwarz–Christoffel conformal mapping, and validity Schottky's conjecture (SC) discussed. authors provide analytical proof SC dimensions upper-stage structure much smaller than those...

Experimental Fowler-Nordheim plots taken from orthodoxly behaving carbon nanotube (CNT) field electron emitters are known to be linear. This shows that, for such emitters, there exists a characteristic enhancement factor (FEF) that is constant range of applied voltages and macroscopic fields $F_\text{M}$. A FEF this kind can evaluated classical CNT emitter models by finite-element other methods, but (apparently contrary experiment) several past quantum-mechanical (QM) calculations find...