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The effect of heating and cooling on the lengths of 1D atomic structures was investigated for the first time by the Monte Carlo method. It is shown that transitions from one equilibrium state to another during heating and cooling are different. It is found that above a certain critical temperature, the experimental system rapidly reaches thermodynamic equilibrium, while below the critical temperature, atomic diffusion is slowed down, and the system remains in a nonequilibrium state, which is observed in most experiments.

We discuss the current state of a promising area of modern physics, the study of the physical properties of metal nanowires and atomic chains. One-dimensional nanostructures are attractive because of both the promise of their practical applications and the possibility of using them to test various theoretical models and approaches by comparing theoretical results with experimental data. We describe experimental conditions under which metal nanowires form on metal and semiconductor surfaces. We give special attention to theoretical models describing the scenario of nanowire growth on various surfaces. We analyze the main experimentally determined factors that affect the distribution of nanowire lengths. We show that the distribution of nanowire lengths on metal and semiconductor surfaces depends not only on external parameters but also on the formation time. We consider the magnetic properties of finite-length atomic chains located on the surfaces of metal and semiconductor crystals. We demonstrate a correlation among the structural, electronic, and magnetic properties of nanowires. We elucidate the effect that nanowires exert on the electronic properties of the surface on which they form. The nature of edge states is explained. The electron states of nanowire atoms are shown to be sensitive to the nanowire length. We discuss the Rashba effect for metal nanowires on a semiconductor surface and analyze how the exchange energy between atoms and the magnetic anisotropy energy affect the macroscopic characteristics of nanowires, such as their critical temperature and the time of spontaneous magnetization reversal.

We present a scanning tunneling microscopy study of decanethiol on Au(001) in the low coverage regime. As expected, the hex reconstruction is lifted, however, no ordered decanethiol phases form. We observe large areas free of Au islands and covered with a disordered decanethiol phase. I(t) spectroscopy measurements suggest that this disordered phase is dynamic and most likely comprises diffusing Au adatoms, decanethiol molecules, and/or Au-adatom-decanethiol molecule complexes. We have performed density functional theory calculations and show that the activation barrier for diffusion is lower when Au-adatom-molecule complexes are considered in comparison to the case of bare molecule. These findings suggest that although no vacancy pits form on Au(001), Au-adatoms expelled during the lifting of the hex reconstruction may be still important for the diffusion of thiol molecules on this surface.

We have studied decanethiolate self-Assembled monolayers on the Au(001) surface. Planar and striped phases, as well as disordered regions, have formed after exposing the Au surface to a decanethiol solution. The planar phases that we observe have a hexagonal symmetry and have not been previously reported for thiols on the Au(001) surface and have lower coverage compared to that of the other known thiol planar phases such as the square α phase. The striped phases that we observe are similar to the previously reported β phase but still feature unit cells that cannot be modeled as the archetype, and the coverage is also somewhat lower. The disordered decanethiolate regions are more dynamic compared to the ordered phases, confirmed with I(t) spectroscopy. This suggests that in these regions the coverage is too low in order to form ordered decanethiolate phases. Our findings contribute to the growing family of possible decanethiol formations on the Au(001) surface, for which still less is known compared to the extensive overview present for the Au(111) surface.

The formation and evolution of one-dimensional atomic structures have been studied by the kinetic Monte Carlo method. It has been found that the distribution of the lengths of such structures depends not only on external parameters but also on the duration of the experiment. It has been revealed that a transition from one equilibrium state to another at heating or cooling occurs through a nonequilibrium state, which is observed in most of the experiments.

We have studied the dynamic behavior of decanethiol and air-oxidized decanethiol self-assembled monolayers (SAMs) on Au(111) using time-resolved scanning tunneling microscopy at room temperature. The air-oxidized decanethiols arrange in a lamellae-like structure leaving the herringbone reconstruction of the Au(111) surface intact, indicating a rather weak interaction between the molecules and the surface. Successive STM images show that the air-oxidized molecules are structurally more stable as compared to the nonoxidized decanethiol molecules. This is further confirmed by performing current-time traces with the feedback loop disabled at different locations and at different molecular phases. Density function theory calculations reveal that the diffusion barrier of the physisorbed oxidized decanethiol molecule on Au(111) is about 100 meV higher than the diffusion barrier of a chemisorbed Au-decanethiol complex on Au(111). A two-dimensional activity map of individual current-time traces performed on the air-oxidized decanethiol phase reveals that all the dynamic events take place within the vacancy lines between the air-oxidized decanethiols. These results reveal that the oxidation of thiols provides a pathway to produce more robust and stable self-assembled monolayers at ambient conditions.

In this paper we present new parameters of the TB-SMA interatomic potentials for the Pt/Cu(111) surface alloy. The parameters are fitted using both the experimental and ab initio data. The potentials reproduce not only the bulk properties of copper and platinum, but also the energy characteristics of the Pt/Cu(111) surface alloy. Growth of the Pt/Cu(111) surface alloy at different Pt concentrations, deposition fluxes, and temperatures is investigated on the atomic scale by performing the self-learning kinetic Monte-Carlo simulations. The main atomic processes responsible for the surface alloy formation and the growth of the finger-like protrusions are identified. The results of our simulations are in a good qualitative agreement with the recent experimental data [J. Chem. Phys. C 118, 3015 (2014)] and can be useful for understanding details of the Pt-Cu interactions at the atomic level.

The kinetic Monte Carlo (kMC) method is an indispensable method for studying atomic and molecular systems, which makes it possible to solve a wide range of problems associated with atomic diffusion, the formation of defects and chemical compounds of various types, as well as the growth and self-organization of nanostructures. In this paper, we consider the fundamentals of the kMC and its modern modifications, both rigid-lattice and off-lattice. Particular attention is focused on constructing self-learning algorithms based on different methods for finding the saddle points of potential energy and on the techniques for the acceleration of the Monte Carlo method. Every considered method is illustrated by relevant examples mostly associated with the physics of metal surfaces.

The growth of one-dimensional atomic chains along the vicinal surface has been studied by the kinetic Monte Carlo method. It has been shown that their growth is determined exclusively by kinetic parameters such as the temperature, flux of deposited atoms, and degree of coating rather than by the binding energy and quantum effects. Conditions under which chains with “magic lengths” appear have been determined.

The pristine Ge(1 1 0) surface is composed of Ge pentagons, which are arranged in relatively large (16 × 2) and c(8 × 10) unit cells. The deposition of sub-monolayer amounts of Au and mild annealing results into de-reconstructed Ge(1 1 0) regions completely free of Ge pentagons and regions composed of nanowires that are aligned along the high symmetry [ 1 1 ¯ 0 ] direction of the Ge(1 1 0) surface. The de-reconstructed Ge(1 1 0) regions consist of atomic rows that are aligned along the [ 1 1 ¯ 0 ] direction. A substantial fraction of these substrate rows are straight and resemble the atom rows of the unreconstructed, i.e. bulk terminated, Ge(1 1 0) surface, whereas the other substrate rows have a meandering appearance. These meandering atom rows are comprised of two types of atoms, one type that appears dim, whereas the other type appears bright in filled-state scanning tunneling microscopy images. Using density functional theory calculations, we have tested more than 20 different atomic models for the meandering atom rows. The density functional theory calculations reveal that it is energetically favorable for the deposited Au atoms to exchange position with Ge atoms in the first layer. Based on these findings we conclude that the bright atoms are Ge atoms, whereas the dim atoms are Au atoms.

A kinetic Monte Carlo method was used to perform large-scale simulation of one-dimensional magnetic nano-structures on vicinal metal surfaces. Temperature ranges for nanochains’ formation were obtained for different systems. The lifetimes of the nanochains were determined, and their stability is discussed. The dependence of chain lifetime on its length is not linear. In order to be usable at room temperature, magnetic Co chains should have a length of 25–30 atoms.

The formation of Co atomic chains on a Cu(775) surface is investigated by the kinetic Monte Carlo method. It is found that the length of Co atomic chains formed as a result of self-organization during epitaxial growth is a random quantity and its mean value depends on the parameters of the experiment. The existence of two structural phases in atomic chains is detected using the density functional theory. In the first phase, the separations between an atom and its two nearest neighbors in a chain are 0.230 and 0.280 nm. In the second phase, an atomic chain has identical atomic spacings of 0.255 nm. It is shown that the temperature of the structural phase transition depends on the length of the atomic chain.

Formation of embedded Co nanostructures in Cu(001) surface under electromigration is investigated on the atomic scale by performing self-learning kinetic Monte Carlo (kMC) simulations. The analysis of simulation results reveals the following important result. The electromigration of vacancies does not influence on the self-organization of Co nanostructures in the first layer of Cu(001) surface at all values of current density, which can be achieved in experiments.

The ab initio calculations are performed to study the structure of atom-wide Co wire on a vicinal Cu{111} surface. We have found two ferromagnetic states of Co wires. In the first state the Co wire consists of dimers, while in the second state the distance between atoms in Co wire is equal. Using Monte Carlo simulations we demonstrated the structure phase transition in a Co wire. Moreover, the phase transition temperature was determined and the size-effect was studied.

Density functional theory and kinetic Monte Carlo method are applied in our study to describe formation, stability and magnetic properties of atom-wide wires on vicinal metal substrate. We present temperature ranges of atom-wide wires’ formation for different systems. The lifetimes of nanowires were determined, and their stability was discussed. Our calculations for both ferromagnetic Fe and Co wires decorating Pt(775) step edge show that the easy magnetization is in the plane perpendicular to the wire, while for Cu(775) it is oriented along the wire. The wire properties obtained from our simulations will be useful both for creating a new generation of materials and for explaining the experimental data.

We present a critical view of the analysis of experimental one-dimensional island size distribution as a function of time. We study the processes of island growth using large-scale kinetic Monte Carlo simulations with diffusion barriers calculated within the framework of the density functional theory. We have shown that one-dimensional island size distribution depends significantly on the time of the experiment. Our model predicts that during annealing or cooling, the transition from one state of thermodynamical equilibrium to another occurs through a non-equilibrium state. This transition consists of Ostwald ripening and decay of one-dimensional islands. The results of our work demonstrate that considering experimental one-dimensional island size distribution as an equilibrium is a big misconception.

Controlled growth of metal monatomic wires would enable on-demand tuning of electronic and magnetic properties in this new class of materials. Prior to this work, it was believed that the binding energy can be determined from the distribution of the lengths of the wires. Another misconception was that the antiripening mechanism or quantum effects are responsible for the growth of wires during postdeposition annealing. Combining kinetic Monte Carlo and first-principles density-functional theory calculations, we study the growth of one-dimensional atomic wires on the steps of vicinal surfaces. We show that for a large value of the bond energy, the antiripening mechanism and quantum effects do not affect the length of metal monatomic wires. The conditions under which wires with magic length appear are determined. The observed mechanism of wire growth will be useful both for explaining the experimental data and for creating atomic wires with a given length.

We have studied the hydrogenation of germanene synthesized on Ge2Pt crystals using scanning tunneling microscopy and spectroscopy. The germanene honeycomb lattice is buckled and consists of two hexagonal sub-lattices that are slightly displaced with respect to each other. The hydrogen atoms adsorb exclusively on the Ge atoms of the upward buckled hexagonal sub-lattice. At a hydrogen exposure of about 100 L, the (1 × 1) buckled honeycomb structure of germanene converts to a (2 × 2) structure. Scanning tunneling spectra recorded on this (2 × 2) structure reveal the opening of a bandgap of about 0.2 eV. A fully (half) hydrogenated germanene surface is obtained after an exposure of about 9000 L hydrogen. The hydrogenated germanene, also referred to as germanane, has a sizeable bandgap of about 0.5 eV and is slightly n-type. © 2018 Author(s).

A zinc-blende (sphalerite) crystallographic structure of SnSi nanocrystals generated by molecular-beam epitaxy is observed by electron microscopy techniques in a Si matrix. Ab initio density-functional modeling reveals a stabilizing effect of the Si matrix, which results in the lowest formation enthalpy of SnSi nanocrystals having the unexpected zinc-blende structure. Such nanocrystals could be applied in Si photonics to function as non-centrosymmetric media for the nonlinear optical process of second harmonic generation.

The self-organization and magnetic properties of small iron and cobalt nanostructures embedded into the first layer of a Cu(100) surface are investigated using the self-learning kinetic Monte Carlo method and density functional theory. The similarities and differences between the Fe/Cu(100) and the Co/Cu(100) are underlined. The time evolution of magnetic properties of a copper monolayer with embedded magnetic atoms at 380 K is discussed.

This study demonstrates how the spin quantum dynamics of a single Fe atom adsorbed on Cu(001) can be controlled and manipulated by the vibrations of a nearby copper tip attached to a nano cantilever by virtue of the dynamic magnetic anisotropy. The magnetic properties of the composite system are obtained from \emph{ab initio} calculations in completely relaxed geometries and turned out to be dependent considerably on the tip-iron distance that changes as the vibrations set in. The level populations, the spin dynamics interrelation with the driving frequency, as well as quantum information related quantities are exposed and analyzed., accepted in New Journal of Physics

The atomic structure of self-organizing iridium (Ir) induced nanowires on Ge(001) is studied by density functional theory (DFT) calculations and variable-temperature scanning tunneling microscopy. The Ir induced nanowires are aligned in a direction perpendicular to the Ge(001) substrate dimer rows, have a width of two atoms and are completely kink-less. Density functional theory calculations show that the Ir atoms prefer to dive into the Ge(001) substrate and push up the neighboring Ge substrate atoms. The nanowires are composed of Ge atoms and not Ir atoms as previously assumed. The regions in the vicinity of the nanowires are very dynamic, even at temperatures as low as 77 K. Time-resolved scanning tunneling microscopy measurements reveal that this dynamics is caused by buckled Ge substrate dimers that flip back and forth between their two buckled configurations.

The energies of magnetic interactions between Co adatoms at the vicinal Cu(111) surface are calculated in the framework of the density functional theory using the Korringa-Kohn-Rostoker type Green’s functions. It is demonstrated that the interactions between Co adatoms appreciably depend on the distance from a surface step. Our calculations show that the magnitude of the repulsive barrier related to the surface step is larger for Co adatoms located at the upper surface terrace than for those located at the lower surface terrace.

The magnetic anisotropy energies, as well as spin and orbital magnetic moments of the atoms involved in the simplest nanostructures formed due to the self-organization within the first Cu(100) surface layer, are calculated in the framework of the density functional theory. The critical role of the surface relaxation, which leads to the rotation of the easy magnetization axis in iron nanoclusters, is demonstrated in the calculations of magnetic anisotropy.

An efficient method has been developed for simulation of the self-organization of metal nanocontacts obtained by transmission electron microscopy. In the framework of this approach, the basic steps of nanocontact formation at room temperature are determined and the main diffusion events determining the contact formation time and the shape of the contacts are revealed. The self-organization of nanocontacts having different orientations with respect to the original fcc lattice is considered. The results obtained are in good agreement with the experimental data on nanocontact formation.

Using a self-learning kinetic Monte-Carlo method, the formation of embedded Co nanostructures is investigated on an atomic scale. The atomic processes responsible for the formation of the simplest types of nanostructures are identified. We demonstrate that the time evolution of the Cu(100) surface with the embedded Co atoms can be divided into three stages. The surface morphology is observed during these three stages at substrate temperatures of 300–400 K and low concentrations of Co atoms. The magnetic properties of the structures forming in the first two stages are calculated using density functional theory. The spin and orbital magnetic moments and the magnetic anisotropy energy of these embedded nanostructures are obtained. In this way, the time evolution of the structural and magnetic properties of a Cu(100) surface with embedded Co atoms is investigated.

The atomic and electronic structures of AgAuAg, AuAgAg, and AuCoCo mixed nanocontacts are investigated by the method of first-principle molecular dynamics. The characteristic interatomic distances in contacts depending on their component composition are determined. The interrelationship between the structural and electronic properties of mixed nanocontacts is shown. The formation of stable bonds between the atoms of various elements in the contact chain, which makes it possible to explain the cause of stabilization and an increase in the contact strength at large interatomic distances is found. It is shown that the addition of Co atoms into pure-gold nanocontacts increases their strength (increases the breaking force of the contact), while the addition of Ag atoms leads to an increase in the range of interatomic distances at which the existence of the nanocontact is possible.

We present our experimental and theoretical study on Co diffusion in the first few atomic layers of Cu(001). While the diffusion of Co atoms in Cu(001) is usually expected to be intense at a temperature $T\ensuremath{\ge}800$ K, in the vicinity of the surface, it is already activated at a considerably lower temperature $T\ensuremath{\sim}650$ K whereas the diffusion in the deep bulk region is still inhibited. This intense near-surface diffusion provides an accumulation of Co atoms in the first six atomic layers upon a single stage Co deposition. The details of the near-surface diffusion are studied by analyzing the distribution of the location depth of the buried single Co atoms. The depth of location of single Co atoms is deduced from scanning tunneling microscopy (STM) data. The subsurface Co atoms induce a perturbation of the electron density of states of the surface which is observable as apparent ringlike ripples in the STM images of the atomically flat Cu surface. The depth of location of the buried Co atoms is determined from the diameter of those rings. The largest amount of Co atoms is found to be in the third layer, emphasizing that the near-surface diffusion should be described by diffusion parameters different from those for bulk diffusion. A model that describes the embedding process of Co atoms into Cu(001) layers is developed. The model assumes Co atoms to diffuse via the vacancy and ring-exchange mechanisms. The energy barriers for the interlayer Co diffusion via those mechanisms are calculated using the nudged elastic band method. The model satisfactorily explains the experimental results. Our study reveals that the energy barriers for Co diffusion in the first five atomic layers of Cu(001) are lower than those in the bulk. This defines the region in which Co diffusion should be considered as a near-surface one.

The mesoscopic relaxation of small Pd islands on Pd(100) and PdH(100) surfaces is investigated on the atomic scale by performing molecular statics calculations. A strong strain and stress inhomogeneity in islands and topmost layers of the substrate is revealed. An unusual size dependence of the shape of islands is discovered.

Electron capture in the collision of a proton with a hydrogen atom is investigated. The probability of electron capture is calculated from first principles by the direct solving of the three-dimensional nonstationary Schrodinger equation. The dependence of the probability of electron capture by a proton on the proton’s velocity and impact parameter is obtained and analyzed thanks to highly efficient computations with the use of graphic processing units.

An investigation of the influence of the sizes of small Co clusters on the Cu(100) surface on the energy barriers of diffusion processes near the clusters and on their surface has been performed using a molecular statics method. The low-temperature mechanism of formation of empty zones near the cluster edges has been established.

The process of the formation of nanocontacts has been studied by the molecular dynamics methods for a group of metals (Cu, Rh, Pd, Ag, Pt, Au). It has been shown that the disruption forces of nanocontacts substantially depend on the orientation ((100), (110), or (111)) of the contact-surface interface. The possibility of forming linear atomic chains as a result of the disruption of nanocontacts has been analyzed for different orientations of the electrode surfaces. The possibility of forming quasi-one-dimensional nanostructures from the Co/Au alloy, which represent a periodic alternation of gold atoms and cobalt trimers, has been predicted.

The aim of our paper is to study the electronic structure of metal island films as examples of a nanosystem. Because the electronic structure is discrete, the charge exchange between atomic particles and nanosystems exhibits quantum-dimensional effects. We calculated the electronic structure of thin island films, which is required for solving and analyzing the problem of charge exchange with the film. The typical island dimensions are also estimated; in the case of dimensions exceeding them, the discreteness of the electronic structure becomes unimportant and quantum-dimensional effects disappear.

The interaction of a palladium nanocontact with a hydrogen molecule has been studied using molecular static method. The influence of impurity on the atomic structure and mechanical properties of the palladium nanocontact has been demonstrated. The characteristic interatomic distance has been determined in this contact. It has been found that the hydrogen molecule dissociates by interaction with nanocontact atoms.

The mechanical properties of extended palladium nanocontacts have been investigated by the molecular dynamics method. The characteristic interatomic distances in the contacts have been determined and the process of the formation of palladium atomic contacts undergoing breaking has been studied for the (100), (110), and (111) orientations of the contact-surface interfaces.

The main mechanisms of the formation of vacancies in the first layer of Cu(100) surface have been investigated by the molecular dynamics method. It has been shown that the interaction of the tip of a scanning tunneling microscope with the surface can increase the intensity of the formation of surface vacancies by a factor of 103−105. On the basis of the reported investigations, an effective method has been proposed for controlling the vacancy concentration in the first layer of Cu(100) surface, which does not imply a change in the temperature of the system.

The formation and evolution of Co islands on Cu(100) surface are studied using molecular dynamics simulation and kinetic Monte Carlo method. Two regimes of cluster growth are found. It is revealed that the transition from one growth regime to another is associated with the formation of rectangular Co islands in the first layer. The dependence of the number of Co atoms in the second layer of the cluster on the Co deposition flux at substrate temperatures of 200 and 300 K is studied.

We study structure and electronic states of Cu nanocontacts. The Korringa–Kohn–Rostoker (KKR) Green’s function method for low-dimensional systems and the density functional theory in the local density approximation are used in our calculations. Atomic relaxations of nanocontacts and electrodes are performed using ab initio based many body potentials constructed by means of the KKR Green’s function method and the tight-binding approach. We demonstrate that nanocontacts exhibit stress oscillations during stretching caused by changes in their structure. Performing ab initio calculations of electronic states in nanocontacts in a fully relaxed geometry, we reveal a strong enhancement in the density of electronic states at the Fermi level before breaking. 2004 Elsevier B.V. All rights reserved.

The formation of embedded Co nanostructures is investigated on the atomic scale by performing self-learning kinetic Monte Carlo simulations. The atomic processes responsible for the formation of small nanostructures are identified. We demonstrate the specific role of the diffusion of dimers at 400 K. The diffusion of dimers leads to the acceleration of the time evolution and the decrease of the chain domination stage.

Density functional theory is used to resolve the adatom-step and adatom–adatom interactions on vicinal Cu(111) surface. We demonstrated that the interactions between 3d adatoms appreciably depend on the distance from a surface step. Our calculations show that the magnitude of the repulsive barrier related to the surface step is larger for 3d adatoms located at the upper surface terrace than for adatoms located at the lower surface terrace.

We report molecular dynamics calculations on the evolution of Co-Au and Ag-Au alloy nanowires stretched along the [100], [110] and [111] crystallographic directions. The strong tendency of chain formation has been found for Ag-Au alloy. On the contrary the Co-Au alloy presents a different breaking pattern. In particular, we have found the formation of tetramer alloy nanowires. Finally, we present the mechanical properties of alloy nanocontacts.

Formation of constrained nanostructures from Co atoms embedded within a Cu(100) surface is investigated on the atomic scale by performing molecular-dynamics and kinetic Monte-Carlo simulations. The atomic processes responsible for the linear and angular chain formations are identified. We demonstrate the key role of substrate vacancies in the motion of embedded Co atoms and investigate the self-organization of Co atoms in different conditions.

The state-of-the-art ab initio calculations are performed to study surface states on stepped Cu(111) surfaces with the terrace widths ranging from $12\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}21\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. In agreement with experiments of Hansmann et al. [Phys. Rev. B 67, 121409(R) (2003)], close to the Fermi energy we reveal electronic states significantly affected by repulsive potential at steps. Our calculations demonstrate that the position of such states is strongly dependent on the terrace width. By using the Kronig-Penney model and ab initio results, the strength of potential barriers at step edges is determined. It is shown that the strength of the confining barriers on Cu(111) vicinals can be significantly affected by decoration of step edges with monatomic Fe wires, similar to recent experimental findings of Shiraki et al. [Phys. Rev. Lett. 92, 096102 (2004)]. Spin-dependent scattering of surface electrons at Fe wires is shown to result in the formation of spin-polarized surface states on stepped Cu(111) surfaces. The majority states remain unaffected. A localization of the minority states at Fe wires suppresses the confinementlike features of the local density of states.