arXiv subjects

Andrey V. Solov'yov

Publications and source records attributed to Andrey V. Solov'yov.

At least 19 recordsLinked to original sources

arXiv2026

Influence of bending parameters on crystalline undulator radiation peak stability for 530 MeV positron channelling

We investigate the stability of crystalline undulator radiation (CUR) peaks emitted by 530 MeV positron channelling in periodically bent C(110) crystals with varying bending amplitudes and bending periods. Relativistic molecular dynamics simulations were performed to quantify how these parameters affect the intensity and position of the CUR peak. The continuous potential approximation was used to identify isolines of constant peak energy, providing a reference for regions of spectral stability. MD results show that increasing the bending amplitude shifts the CUR peak to lower photon energies, while decreasing the period shifts it to higher energies, with both trends accompanied by enhanced dechannelling. For crystal parameters similar to recent experiments conducted at the MAinz MIkrotron (MAMI), the simulated CUR peak appears near 0.515 MeV. These results demonstrate that the CUR peak remains stable across a broad range of bending amplitudes and periods, providing quantitative estimates of the sensitivity of the emitted radiation to variations in the crystal bending parameters.

physics.acc-ph↗

arXiv2026

Structural effects of boron doping in diamond crystals for gamma-ray light-source applications: Insights from molecular dynamics simulations

Boron-doped diamond crystals (BDD, C$_{1-x}$B$_{x}$) exhibit exceptional mechanical strength, electronic tunability, and resistance to radiation damage. This makes them promising materials for use in gamma-ray crystal-based light sources. To better understand and quantify the structural distortions introduced by doping, which are critical for maintaining channelling efficiency, we perform atomistic-level molecular dynamics simulations on periodic C$_{1-x}$B$_{x}$ systems of various sizes. These simulations allow the influence of boron concentration on the lattice constant and the (110) and (100) inter-planar distances to be evaluated over the concentration range from pure diamond (0%) to 5% boron at room temperature (300 K). Linear relationships between both lattice constant and inter-planar distance with increasing dopant concentration are observed, with a deviation from Vegard's Law. This deviation is larger than that reported by other theoretical and computational studies; however, this may be attributed to an enhanced crystal quality over these studies, a vital aspect when considering gamma-ray crystal light source design. The methodology presented here incorporates several refinements to closely reflect the conditions of microwave plasma chemical vapour deposition (MPCVD) crystal growth. Validation of the methodology is provided through a comprehensive statistical analysis of the structure of our generated crystals. These results enable reliable atomistic modelling of doped diamond crystals and support their use in the design and fabrication of periodically bent structures for next-generation gamma-ray light source technologies.

cond-mat.mtrl-sci↗

arXiv2026

The impact of experimental conditions on the observation of channeling and crystalline undulator radiation

In this study, we present a comprehensive quantitative analysis of the radiation emitted by 855 MeV electrons propagating through an oriented diamond hetero-crystal. The crystal consists of two distinct segments: (i) a straight single-crystal diamond substrate, and (ii) a diamond layer that is periodically doped with boron atoms. The doping profiles were derived from precise experimental measurements of boron concentration obtained during the layer fabrication via Microwave Plasma Chemical Vapor Deposition (MPCVD). Our study systematically investigates the channelling and the crystalline undulator radiation, accounting for the different doping profiles in the undulating region. The simulations were conducted using the advanced MBNExplorer software package, which enables detailed modeling of particle trajectories and radiation emission. We report on good agreement with experiment and discuss remaining discrepancies providing possible explanations for them. The results obtained show that the radiation intensity is significantly affected by a range of factors, including the angular divergence of the incident beam, its orientation with respect to the target, the direction in which the emitted radiation is detected, and the choice of the doping profiles. These findings are important for optimising the design of crystalline undulators as novel gamma radiation light sources.

physics.acc-ph↗

arXiv2026

Scaling Dependencies in Irradiation-Driven Molecular Dynamics Simulations: Case Study of W(CO)$_6$ Fragmentation

Irradiation-driven fragmentation and chemical transformations of organometallic molecules play a central role in nanofabrication techniques based on the use of focused charged-particle beams. In this paper, the electron irradiation-induced fragmentation dynamics of W(CO)$_6$, a commonly used precursor for focused electron beam-induced deposition (FEBID), is investigated using the irradiation-driven molecular dynamics (IDMD) method. Simulations are performed for gas-phase systems with different precursor densities and under different irradiation conditions. The results reveal progressive fragmentation of W(CO)$_6$ molecules into W(CO)$_n$ species, accompanied by the formation of W-rich molecular clusters. The evolution of fragment abundances shows a strong dependence on both precursor density and electron fluence. Higher densities and larger fluences result in more extensive fragmentation and promote the aggregation of tungsten atoms into small metal clusters. Under certain irradiation conditions, the studied molecular systems evolve towards a steady state characterised by slightly varying fragment abundances. The obtained scaling relations between irradiation parameters and fragment distributions provide guidance for selecting simulation parameters in IDMD simulations of the FEBID process, ensuring a quantitative description of precursor fragmentation dynamics.

physics.atm-clus↗

arXiv2025

The impact of ionising collisions on channeling and radiation emission for high-energy electrons and positrons

This paper presents a quantitative analysis of the impact of inelastic collisions with atoms in a crystalline environment on the channeling efficiency and intensity of the channeling radiation for high-energy electrons and positrons passing through oriented crystalline targets. This analysis is based on numerical simulations of the channeling process, which were performed using the MBN Explorer software package. Ionising collisions are considered random, fast and local events, and are incorporated into the classical relativistic molecular dynamics framework according to the previously described algorithm. The case studies presented refer to 10 GeV electrons and positrons incident on single crystals of diamond and silicon, oriented along the (110) and (111) planes, with thicknesses of up to 1 mm for electrons and 6 mm for positrons. To elucidate the role of ionising collisions, simulations were performed with and without accounting for them. It is shown that, for electrons, both approaches lead to similar results with regard to both the channelling efficiency and the radiation intensity. In practical terms, this means that numerical simulations can be carried out without accounting for ionising collisions, which are much faster yet produce similar results. For positrons, the ionising collisions reduce significantly the channeling efficiency. However, their impact on the radiation intensity strongly depends on the opening angle of the cone within which the radiation emission is collected. A quantitative analysis of this feature is presented in the paper.

physics.acc-ph↗

arXiv2025

Stochastic dynamics simulation of the focused electron beam induced deposition process

This work reports on the development of a new approach to the multiscale computational modelling of the focused electron beam-induced deposition (FEBID), realised using the advanced software packages: MBN Explorer and MBN Studio. Our approach is based on stochastic dynamics (SD), which describes the probabilistic evolution of complex systems. The parameters for the new SD-based FEBID model were determined using molecular dynamics (MD) simulations. A new methodology was developed for this purpose and is described in detail. This methodology can be applied to many other case studies of the dynamics of complex systems. Our work focuses on the FEBID process involving W(CO)$_6$ precursor molecules deposited on a hydroxylated SiO$_2$-H substrate. Simulations and a detailed analysis of a growing W-rich nanostructure were performed. This new approach was shown to provide essential atomistic insights into the complex FEBID process, including the elemental composition and morphology of the deposit at each stage of growth. The derived results were then compared with experimental observations and validated. The multiscale methods developed in this study can be further upgraded and applied to important technological developments, such as 3D nanoprinting.

physics.comp-ph↗

arXiv2025

Electron and positron channeling and photon emission processes in boron doped periodically bent diamond

In this paper, theoretical and numerical analyses are conducted of the profiles of the planar (-110) crystallographic direction in the diamond layer doped with boron atoms. The planar profiles for periodic doping following several ideal dependencies of the boron concentration on the distance in the crystalline medium. Numerical simulations of the channeling and photon emission processes have been carried out for 855 MeV electron and 530 MeV positron beams incident on boron-doped diamond with a four-period bending profile in the samples grown at the European Synchrotron Radiation Facility (ESRF). The simulations were performed using the MBN Explorer software package. It is shown that the channeling efficiency and the intensity of the crystalline undulator radiation strongly depend on the orientation of the incident beam relative to the bent channel profile at the entrance to the boron-doped layer. For the same conditions at the crystal entrance, the intensity of radiation emitted by positrons is significantly higher than that for electrons.

physics.acc-ph↗

arXiv2024

Positron Channeling in Quasi-Mosaic Bent Crystals: Atomistic Simulations vs. Experiment

This paper reports on a comprehensive study of an ultra-relativistic positron beam deflection by an oriented quasi-mosaic crystal. The analysis was carried out for the positron energy of 530 MeV incident on the quasi-mosaic bent Si(111) crystal. This particular case was chosen because it has recently been studied experimentally at the Mainz Microtron MAMI. The results of the relativistic molecular dynamics simulations were compared with the experimental observations and a good agreement was found. The presence of planar channeling, de-channeling, volume reflection and volume capture processes in the angular distribution of deflected positrons for different beam-crystal alignments has been studied. Predictions have been made for certain crystal orientations for which experimental data are lacking.

physics.atom-ph↗

arXiv2024

Narrowband gamma-ray radiation generation by acoustically driven crystalline undulators

In this paper we present a novel scheme for the controlled generation of of tunable narrowband gamma-ray radiation by ultra-relativistic positron beams inside acoustically driven periodically bent crystals. A novel acoustic crystalline undulator is presented, in which excitation of a silicon single crystal along the (100) planar direction by a piezoelectric transducer periodically modulates the crystal lattice in the [100] axial direction. An ultra-relativistic positron beam is directed diagonally into the crystal and propagates along the (110) planes. The lattice modulation forces the positrons to follow periodic trajectories,resulting in the emission of undulator radiation in the MeV range. A computational methodology for the design and development of such acoustically based light sources is presented together with the results of simulations demonstrating the favourable properties of the proposed technology. The longitudinal acoustic strains induced in the crystal by high-frequency piezoelectric elements are calculated by finite element simulations. The resulting bending profiles of the deformed crystal planes are used as geometrical conditions in the relativistic molecular dynamics simulations that calculate the positron trajectories and the spectral distribution of the emitted radiation. The results show a strong enhancement of the emitted radiation within a narrow spectral band defined by the bending period, demonstrating the feasibility and potential of the proposed technology.

physics.acc-ph↗

arXiv2024

Intensive gamma-ray light sources based on oriented single crystals

The feasibility of gamma-ray light sources based on the channeling phenomenon of ultra-relativistic electrons and positrons in oriented single crystals is demonstrated using rigorous numerical modeling. Case studies are presented for 10 GeV and sub-GeV $e^{-}/e^{+}$ beams incident on $10^{-1}-10^0$ mm thick diamond and silicon crystals. It is shown that for moderate values of the beam average current ($\lesssim 10$ $μ$A) the average photon flux in the energy range $10^0-10^2$ MeV emitted within the $10^1-10^3$ $μ$rad cone and 1 \% bandwidth can be on the level of $10^{10}$ photon/s for electrons and $10^{10}-10^{12}$ photon/s for positrons. These values are higher than the fluxes available at modern laser-Compton gamma ray light sources.

physics.acc-ph↗

arXiv2024

Dopant concentration effects on Si$_{1-x}$Ge$_{x}$ crystals for emerging light-source technologies: A molecular dynamics study

In this study, we conduct atomistic-level molecular dynamics simulations on fixed-sized silicon-germanium (Si$_{1-x}$Ge$_{x}$) crystals to elucidate the effects of dopant concentration and temperature on the crystalline inter-planar distances. Our calculations consider a range of Ge dopant concentrations between pure Si (0%) and 15%, and for both the optimised system state and a temperature of 300 K. We observe a linear relationship between Ge concentration and inter-planar distance and lattice constant, in line with the approximation of Vegard's Law, and other experimental and computational results. These findings will be employed in conjunction with future studies to establish precise tolerances for use in crystal growth, crucial for the manufacture of crystals intended for emerging gamma-ray crystal-based light source technologies.

physics.atom-ph↗

arXiv2023

Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment

This paper reviews the new highly interdisciplinary research field studying the behavior of condensed matter systems exposed to radiation. The paper highlights several relevant examples of recent advances in the field and provides a roadmap for the development of the field in the next decade. Condensed matter systems exposed to radiation may have very different natures, being inorganic, organic or biological, finite or infinite, be composed of many different molecular species or materials, existing in different phases (solid, liquid, gaseous or plasma) and operating under different thermodynamic conditions. The essential and novel element of this research is that, despite the vast diversity of such systems, many of the key phenomena related to the behavior of irradiated systems (such as radiation-induced damage, mechanisms of damage repair and control, radiation protection, etc.) are very similar and can be understood based on the same fundamental theoretical principles and computational approaches. One of the essential features of the aforementioned phenomena concerns their multiscale nature as the manifestation of the radiation-induced effects occurring at different spatial and temporal scales ranging from the atomic to the macroscopic. The multiscale nature of the effects and similarity of their manifestation in systems of different origins necessarily brings together different disciplines, such as physics, chemistry, biology, materials and nano-science, and biomedical research, demonstrating numerous interlinks and commonalities between them. This research field is highly relevant to many novel and emerging technologies and medical applications.

physics.chem-ph↗

arXiv2023

Computational characterization of novel nanostructured materials: A case study of NiCl$_2$

A computational approach combining dispersion-corrected density functional theory (DFT) and classical molecular dynamics is employed to characterize the geometrical and thermo-mechanical properties of a recently proposed 2D transition metal dihalide NiCl$_2$. The characterization is performed using a classical interatomic force field whose parameters are determined and verified through the comparison with the results of DFT calculations. The developed force field is used to study the mechanical response, thermal stability, and melting of a NiCl$_2$ monolayer on the atomistic level of detail. The 2D NiCl$_2$ sheet is found to be thermally stable at temperatures below its melting point of ~695 K. At higher temperatures, several subsequent structural transformations of NiCl$_2$ are observed, namely a transition into a porous 2D sheet and a 1D nanowire. The computational methodology presented through the case study of NiCl$_2$ can also be utilized to characterize other novel 2D materials, including recently synthesized NiO$_2$, NiS$_2$, and NiSe$_2$.

cond-mat.mtrl-sci↗

arXiv2023

Mechanisms of radiation-induced structural transformations in deposited gold clusters

Physical mechanisms of structural transformations in deposited metallic clusters exposed to an electron beam of a transmission electron microscope (TEM) are studied theoretically and computationally. Recent TEM experiments with size-selected Au$_{923}$ clusters softly deposited on a carbon substrate showed that the clusters undergo structural transformations from icosahedron to decahedron and face-center cubic (fcc) structures upon exposure to a 200-keV electron beam. In this paper, we demonstrate that the relaxation of collective electronic (plasmon) excitations formed in deposited metal clusters can induce the experimentally observed structural transformations. Such excitations in the clusters are formed mainly due to the interaction with low-energy secondary electrons emitted from a substrate. The characteristic occurrence times for plasmon-induced energy relaxation events are several orders of magnitude shorter than those for the momentum transfer events by energetic primary electrons to atoms of the cluster. The theoretical analysis is complemented by molecular dynamics simulations, which show that an icosahedral Au$_{923}$ cluster softly deposited on graphite is transformed into an fcc-like structure due to the vibrational excitation of the cluster.

physics.atm-clus↗

arXiv2023

Neuromorphic nanocluster networks: Critical role of the substrate in nano-link formation

Atomic cluster-based networks represent a promising architecture for the realization of neuromorphic computing systems, which may overcome some of the limitations of the current computing paradigm. The formation and breakage of synapses between the clusters are of utmost importance for the functioning of these computing systems. This paper reports the results of molecular dynamics simulations of synapse (bridge) formation at elevated temperatures and thermal breaking processes between 2.8 nanometer-sized Au$_{1415}$ clusters deposited on a carbon substrate, a model system. Crucially, we find that the bridge formation process is driven by the diffusion of gold atoms along the substrate, however small the gap between the clusters themselves. The complementary simulations of the bridge-breaking process reveal the existence of a threshold bias voltage to activate bridge rupture via Joule heating. These results provide an atomistic-level understanding of the fundamental dynamical processes occurring in neuromorphic cluster arrays.

physics.atm-clus↗

arXiv2023

Molecular dynamics simulation of nanofilament breakage in neuromorphic nanoparticle networks

Neuromorphic computing systems may be the future of computing and cluster-based networks are a promising architecture for the realization of these systems. The creation and dissolution of synapses between the clusters are of great importance for their function. In this work, we model the thermal breakage of a gold nanofilament located between two gold nanoparticles via molecular dynamics simulations to study on the mechanisms of neuromorphic nanoparticle-based devices. We employ simulations of Au nanowires of different lengths ($2-8$ nm), widths ($0.4-0.8$ nm) and shapes connecting two Au$_{1415}$ nanoparticles (NPs) and monitor the evolution of the system via a detailed structural identification analysis. We found that atoms of the nanofilament gradually aggregate towards the clusters, causing the middle of the wire to gradually thin and then break. Most of the system remains crystalline during this process but the center is molten. The terminal NPs increase the melting point of the NWs by fixing the middle wire and act as recrystallization areas. We report a strong dependence on the width of the NWs, but also their length and structure. These results may serve as guidelines for the realization of cluster-based neuromorphic computing systems.

physics.atm-clus↗

arXiv2023

Topical Issue "Dynamics of Systems on the Nanoscale (2021)". Editorial

Exploration of the structure formation and dynamics of animate and inanimate matter on the nanometer scale is a highly interdisciplinary field of rapidly emerging research. It is relevant for various molecular and nanoscale systems of different origins and compositions and concerns numerous phenomena originating from physics, chemistry, biology, and materials science. This topical issue presents a collection of research papers devoted to different aspects of the Dynamics of Systems on the Nanoscale. Some of the contributions discuss specific applications of the research results in several modern and emerging technologies, such as controlled nanofabrication with charged particle beams or the design and practical realization of novel gamma-ray crystal-based light sources. Most works presented in this topical issue were reported at the joint Sixth International Conference "Dynamics of Systems on the Nanoscale" and the tenth International Symposium "Atomic Cluster Collisions" (DySoN-ISACC 2021), which were held in Santa Margherita Ligure, Italy, in October 2021.

physics.chem-ph↗

arXiv2023

Atomistic modelling and structural characterisation of coated gold nanoparticles for biomedical applications

This study presents the results of atomistic structural characterisation of 3.7 nm diameter gold nanoparticles (NP) coated with polymer polyethylene glycol (PEG)-based ligands of different lengths (containing $2-14$ monomers) and solvated in water. The system size and composition are selected in connection to several experimental studies of radiosensitisation mechanisms of gold NPs. The coating structure and water distribution near the NP surface are characterised on the atomistic level by means of molecular dynamics simulations. The results of simulations carried out in this study, combined with the results of our recent study [J. Phys. Chem. A 126 (2022) 2170] and those from the field of polymer physics, are used to calculate key structural parameters of the coatings of radiosensitising gold NPs. On this basis, connections between the coating structure and distribution of water are established for different NP sizes as well as lengths and surface densities of coating molecules. The quantitative analysis of water distribution in the vicinity of coated metal NPs can be used to evaluate the radiosensitising effectiveness of a particular NP system based on the proximity of water to the NP metal core, which should impact the production of hydroxyl radicals and reactive oxygen species in the vicinity of metal NPs exposed to ionising radiation.

physics.atm-clus↗