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Dynamical processes of low-energy carbon ion collision with the graphene supported by diamond
摘要： The dynamical processes of a low-energy carbon ion collision with the graphene sheet supported by diamond at three impact positions are studied by using empirical potential molecular dynamics simulations. The energy transformation and the structural evolution have been studied. Five types of processes are observed: adsorption, hybridization, defects formation in diamond, atom emission and transmission. We find that the irradiation damage is closely related to the incident energy and impact position. In our simulations, as the projectile collides at a graphene atom, it transfers most of its energy to the primary knock-on atom, and defects are created in graphene. When the projectile moves perpendicular towards the center of a C-C bond in the graphene sheet, the energy transferred from the projectile to the atoms associated with the bond increases firstly and then decreases with the increasing incident energy, and the graphene sheet remains two-dimensional crystal structure after collision when the incident energy is larger than 360 eV. While the impact location is the center of a hexagonal ring on the graphene sheet, the energy transferred from the projectile to the atoms of the target ring is very small regardless of how large is the incident energy, and the graphene sheet is able to keep perfect crystal structure when the incident energy is larger than 34 eV.
关键词： diamond,carbon ion collision,graphene,irradiation damage,molecular dynamics simulations
更新于2025-09-09 09:28:46
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Thermal conductivity of TiO<sub>2</sub> nanotube: A molecular dynamics study
摘要： The thermal conductivity of anatase TiO2 nanotubes was investigated using equilibrium molecular dynamics simulations based on Green-Kubo formalism. The calculated thermal conductivity of ~8.16 W/K ? m for anatase crystal at room temperature agrees well with experimental value of ~8.5 W/K?m, demonstrating that the method used in our calculation can provide a good description for the thermal transport of TiO2. The dependence of the thermal conductivity of TiO2 nanotubes with temperature, tube size and chirality were studied in detail. The relationship between the thermal conductivity and the vibrational density-of-states of the nanotubes was also investigated.
关键词： Molecular dynamics simulations,Thermal conductivity,Nanotube structure
更新于2025-09-09 09:28:46
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Detachment Dynamics of Graphene Nanoribbons on Gold
摘要： Metal-surface physisorbed graphene nanoribbons (GNRs) constitute mobile nanocontacts whose interest is simultaneously mechanical, electronic, and tribological. Previous work showed that GNRs adsorbed on Au(111) generally slide smoothly and superlubrically owing to incommensurability of their structures. We address here the nanomechanics of detachment, such as realized when one end is picked up and lifted by an AFM cantilever. AFM nanomanipulations and molecular-dynamics (MD) simulations identify two successive regimes, characterized by (i) a progressively increasing local bending, accompanied by the smooth sliding of the adhered part, followed by (ii) a stick-slip dynamics involving sudden bending relaxation associated to intermittent jumps of the remaining adhered GNR segment and tail end. AFM measurements of the vertical force exhibit oscillations which, compared with MD simulations, can be associated to the successive detachment of individual GNR unit cells of length 0.42 nm. Extra modulations within one single period are caused by step-like advancements of the still-physisorbed part of the GNR. The sliding of the incommensurate moir′e pattern that accompanies the GNR lifting generally yields an additional long-period oscillation: while almost undetectable when the GNR is aligned in the standard “R30” orientation on Au(111), we predict that such feature should become prominent in the alternative rotated “R0” orientation on the same surface, or on a different surface, such as perhaps Ag(111).
关键词： molecular-dynamics simulations,gold,AFM,graphene nanoribbons,detachment dynamics
更新于2025-09-04 15:30:14
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Building two-dimensional materials one row at a time: Avoiding the nucleation barrier
摘要： Assembly of two-dimensional (2D) molecular arrays on surfaces produces a wide range of architectural motifs exhibiting unique properties, but little attention has been given to the mechanism by which they nucleate. Using peptides selected for their binding affinity to molybdenum disulfide, we investigated nucleation of 2D arrays by molecularly resolved in situ atomic force microscopy and compared our results to molecular dynamics simulations. The arrays assembled one row at a time, and the nuclei were ordered from the earliest stages and formed without a free energy barrier or a critical size. The results verify long-standing but unproven predictions of classical nucleation theory in one dimension while revealing key interactions underlying 2D assembly.
关键词： two-dimensional materials,atomic force microscopy,nucleation,peptides,molecular dynamics simulations
更新于2025-09-04 15:30:14
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Medium range order and configurational entropy of vitreous silica
摘要： Two potential sets and three thermodynamic regimes were utilized in molecular dynamics simulations in the preparation of the corresponding structures of vitreous silica. Medium range order characterized by means of basic ring distributions is robust to both thermodynamic conditions and/or potentials sets. A strong correlation between topology and geometry is demonstrated; the correlation is much stronger for simple clusters/small rings. Configurational entropy was evaluated by the ideal mixing of the structural units of the decomposed silica network. Entropy responds to alterations in the heating/cooling rates and its behaviour yields an excellent agreement with the experimental specific heat capacity drops observed at the glass transition. It is suggested the glass transition of the simulated glass should be identified with the change of entropy and not with a change of enthalpy as is conventionally done.
关键词： medium range order,configurational entropy,vitreous silica,glass transition,molecular dynamics simulations
更新于2025-09-04 15:30:14
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Effect of the anchoring strength on the phase behaviour of discotic liquid crystals under face-on confinement
摘要： In this study we have performed molecular dynamics simulations to study a Gay-Berne discotic fluid confined in a slab geometry for a fixed confinement length. Four different anchoring strengths with a homeotropic (face-on) configuration were studied. We found that changing the anchoring strength changes the normal component of the stress tensor, which in turn changes the density of the system’s bulk. This phenomenon leads to a shift in the isotropic-nematic transition temperature. We observe that the temperature regions where the nematic phase is present diminishes as the anchoring strength increases. The anchoring strength also affects the nematic-columnar coexistence temperature-region: it spans over more temperatures at higher anchoring strengths.
关键词： molecular dynamics simulations,discotic liquid crystals,anchoring strength,phase behaviour,face-on confinement
更新于2025-09-04 15:30:14
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The effects of curvature on the thermal conduction of bent silicon nanowire
摘要： Curvature induced by mechanical deformation in nanostructures has been found to significantly affect their stability and reliability during applications. In this work, we investigated the effects of curvature induced by mechanical bending on the thermal properties of silicon nanowire (SiNW) by using molecular dynamics simulations. By examining the relationship between the curved geometry and local temperature/heat flux distribution, we found that there is no temperature gradient/heat flux along the radial direction of the bent SiNW, and the local heat current density along the circumferential direction varies with the radius of curvature. Interestingly, a ～10% reduction in the thermal conductivity is found in the bent SiNW due to the depression of long-wavelength phonons caused by its inhomogeneous deformation. The present work demonstrates that the curvature induced by mechanical bending can be used to modulate the thermal conductivity of SiNWs.
关键词： thermal conductivity,curvature,silicon nanowire,thermal conduction,molecular dynamics simulations
更新于2025-09-04 15:30:14