Empirical Many-body Potential Energy Function Research Articles

Embryonic Iridium nanoclusters (n=3–13): A molecular dynamics computer simulation

The determination of the physical and chemical properties of small nanoparticles plays a fundamental role in homogeneous and heterogeneous catalysis since a large number of the surface atoms of these nanoparticles can be exposed to chemical reactions, as well as in chemisorption, solid state physics, laser physics, crystal growth, epitaxy and surface science in general as most recent experimental and theoretical investigations have been disclosed. An empirical many-body Potential Energy Function (PEF) incorporating two-plus three-body atomistic potential derived by fitting experimental data pertaining to bulk Iridium has been applied to study the structural stability and energetics of Iridium nanoparticles of Irn([Formula: see text]–13). A constant temperature Molecular Dynamics (MD) technique is employed in the simulations. It is found that the energetically most stable structures of Iridium nanoparticles are in three-dimensional distorted compact forms close to symmetric geometries with the MD technique. The theoretical predictions are compared to the available theoretical and experimental literature data for binding energies, bond lengths and the most stable nanocluster geometry.

Size, Shape and Structure Dependent Cohesive Energy of Gold Nanoparticles: Empirical Many-Body Potential Energy Function Calculations

A thermodynamic model based on an empirical many-body potential energy function is used, to investigate the stability and energetic features of gold nanoparticles as a function of both size and shape. The concept of a localized atomic bond for surface atoms, and a non-relaxed atomic bond for the interior atoms is used. Among the five different investigated shapes, the qualitative behaviour for the cohesive energy per atom of gold nanoparticles with size range 200 1000 atoms, the general behaviour prefers; sphere < cubic <cuboctahedron < truncated octahedron < octahedron. On the other hand, the surface energy for gold nanoparticles is observed to be prominent in the nano-scale and it differs from shape to another, and falls down fast in the size range 200 < n < 1000 atoms having general trend; sphere < cubic <octahedron < truncated octahedron < cuboctahedron.

Molecular dynamics simulation study of the diamond D5 substructures

Abstract Diamond D5 is the name proposed by Diudea for hyper-diamonds having their rings mostly pentagonal. Within D5, in crystallographic terms: the mtn structure, known in clathrates of type II, several substructures can be defined. In the present work, the structural stability of such intermediates/fragments appearing in the construction/destruction of D5 net was investigated using molecular dynamics simulation. Calculations were performed using an empirical many-body potential energy function for hydrocarbons. It has been found that, at normal temperature, the hexagonal hyper-rings are more stable while at higher temperature, the pentagonal ones are relatively more resistant against heat treatment.

Cluster, Surface and Bulk Properties of ZnCd Binary Alloys: Molecular-Dynamics Simulations

The structural and electronic properties of isolated neutral ZnmCdn clusters for m+n £ 3 have been investigated by performing density functional theory calculations at B3LYP level. The optimum geometries, vibrational frequencies, electronic structures, and the possible dissosiation channels of the clusters considered have been obtained. An empirical many-body potential energy function (PEF), which comprices two- and three-body atomic interactions, has been developed to investigate the structural features and energetics of ZnmCdn (m+n=3,4) microclusters. The most stable structures were found to be triangular for the three-atom clusters and tetrahedral for the four-atom clusters. On the other hand, the structural features and energetics of Znn-mCdm (n=7,8) microclusters, and Zn50, Cd50, Zn25Cd25, Zn12Cd38, and Zn38Cd12 nanoparticles have been investigated by performing molecular-dynamics computer simulations using the developed PEF. The most stable structures were found to be compact and three-dimensional for all elemental and mixed clusters. An interesting structural feature of the mixed clusters is that Zn and Cd atoms do not mix in mixed clusters, they come together almost without mixing. Surface and bulk properties of Zn, Cd, and ZnCd systems have been investigated too by performing molecular-dynamics simulations using the developed PEF. Surface reconstruction and multilayer relaxation on clean surfaces, adatom on surface, substitutional atom on surface and bulk materials, and vacancy on surface and bulk materials have been studied extensively.

Correlations between the energetics of ZnCd nanoparticles and some of their corresponding bulk properties: molecular-dynamics simulations

The structural stability of Zn 50, Cd 50, Zn 25Cd 25, Zn 12Cd 38, and Zn 38Cd 12 nanoparticles has been investigated by performing molecular-dynamics computer simulations using a recently developed empirical many-body potential energy function. The most stable structures were found to be compact and three dimensional for both elemental and mixed clusters. An interesting structural feature of the mixed clusters is that Zn and Cd atoms do not mix, especially at proportions around the corresponding alloy eutectic composition, they come together almost without mixing.

Titanium coverage on a single-wall carbon nanotube: molecular dynamics simulations

The minimum energy structures of Ti covered (8,0) single-wall carbon nanotube (SWNT) have been investigated theoretically. Using available experimental data and the results of density functional theory calculations, we first parametrized a reliable empirical many-body potential energy function (PEF) for the CTi binary system. The PEF used in the calculations includes two- and three-body atomic interactions. Then performing molecular dynamics simulations at 1 and 300 K, we obtained the minimum-energy configurations for Ti covered (8,0)-SWNT. The configurations reported here include low and high coverage of Ti on nanotubes. We have found that one layer of Ti did not distort the nanotube significantly, whereas two-layer coverage showed an interesting feature: the second layer of Ti pushed the first layer inside the wall of nanotube, but the general shape of the nanotube was not affected so much.

Molecular‐dynamics simulations of surface and bulk properties of Zn, Cd, and ZnCd systems

AbstractSurface and bulk properties of Zn, Cd, and ZnCd systems have been investigated by performing molecular‐dynamics simulations using a recently developed empirical many‐body potential energy function for these systems, which comprices two‐ and three‐body atomic interactions. Surface reconstruction and multilayer relaxation on clean surfaces, adatom on surface, substitutional atom on surface and bulk materials, and vacancy on surface and bulk materials have been studied extensively. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

STRUCTURAL FEATURES AND ENERGETICS OF ZnkCdl MICROCLUSTERS

An empirical many-body potential energy function has been developed to investigate the structural features and energetics of Zn k Cd l (k+l=3, 4) microclusters. The most stable structures were found to be triangular for the three-atom clusters and tetrahedral for the four-atom clusters. The present results are in good agreement with available literature values.

STRUCTURAL PROPERTIES OF DIAMOND NANORODS: MOLECULAR-DYNAMICS SIMULATIONS

The structural properties of carbon nanorods obtained from diamond crystal have been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. Diamond nanorods have been generated from three low-index planes of diamond crystal. It has been found that the average coordination number, cross-section geometry, and surface orientation from which the nanorod is generated play a role in the stability of diamond nanorods under heat treatment. The most stable diamond nanorod has been obtained from the (111) surface.

GOLD DEPOSITION ON GaAs(001) SURFACES: MOLECULAR-DYNAMICS SIMULATIONS

We have simulated the gold deposition on arsenic and gallium terminated GaAs(001) surfaces at low and room temperatures. It has been found that gallium terminated surface is relatively less stable in comparison to the arsenic terminated surface. On the other hand, a single gold adatom on the surface has different characteristics than full coverage gold atoms on the surface; a single gold atom diffuses into the surface at room temperature. Simulations have been performed by considering classical molecular-dynamics technique using an empirical many-body potential energy function comprising two- and three-body atomic interactions.

STRUCTURAL PROPERTIES OF CARBON NANORODS: MOLECULAR-DYNAMICS SIMULATIONS

The formation of carbon nanorods from various types of carbon nanotubes has been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanorod formed from carbon nanotubes with different chirality is not stable even at low temperature.

Stability of Carbon Nanoonion C20@C60@C240: Molecular Dynamics Simulations

The structural stability of carbon nanoonion C20@C60@C240 has been investigated by performing molecular dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanoonion is not so resistive against heat treatment, nor is it as strong as isolated single carbon nanoballs. Although single nanoballs resist heat treatment up to 4300 K, nanoonion disintegrates after 2600 K.

STRUCTURAL AND ELECTRONIC PROPERTIES OF CARBON NANOBALLS: C20, C60, AND C20@C60

The structural stability of carbon nanoballs (fullerenes) C 20, C 60, and onion type C 20@ C 60 has been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that C 20 is relatively resistive to heat treatment, however, the onion type structure is relatively less strong against heat treatment. The electronic structure of the systems considered has been also studied by performing density functional theory type calculations.

EFFECT OF CHIRALITY ON THE STABILITY OF CARBON NANOTUBES: MOLECULAR-DYNAMICS SIMULATIONS

The effect of chirality on the structural stability of single-wall carbon nanotubes have been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanotube in chiral structure is more stable under heat treatment relative to zigzag and armchair models. The diameter of the tubes is slightly enlarged under heat treatment.

MOLECULAR-DYNAMICS SIMULATIONS OF CARBON NANOCAGE STRUCTURES: NANOBALLS AND NANOTOROIDS

The structural stability of carbon nanocages, fullerens and toroids, have been investigated by performing molecular-dynamics computer simulations. The systems considered are C 120 and C 240 in ball and toroidal structures. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that C 120 ball is very unstable, and the other structures are relatively more strong against heat treatment.

FROM CARBON NANOTUBES TO CARBON NANORODS

The structural properties of single and multi-wall carbon nanotubes and the formation of carbon nanorods from multi-wall carbon nanotubes have been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanorod formation takes place with smallest possible multi-wall nanotubes under heat treatment. On the other hand, it has been also found that single-wall carbon nanotubes are stronger than the multi-wall nanotubes against heat treatment.

ENERGETICS OF ARSENIC TERMINATED GaAs(001) SURFACES

We have investigated systematically the energetics of arsenic terminated GaAs(001) surfaces. Available surface models proposed in the literature have been considered, and relaxation and surface energies of each model have been calculated using an empirical many-body potential energy function comprising two and three-body atomic interactions.

Modelling gold clusters with an empirical many-body potential

Molecular Dynamics Simulated Annealing has been used to probe the structure of small Au clusters consisting of between 2 and 40 atoms. The interatomic interactions within these clusters are described using an empirical Murrell-Mottram many-body potential energy function. Four distinct structural motifs are present in the structures of the predicted global minima, based on octahedra, decahedra, icosahedra and hexagonal prisms.

THE EFFECT OF PBC ON THE SIMULATION OF NANOTUBES

The effect of the periodic boundary condition (PBC) on the structure and energetics of nanotubes has been investigated by performing molecular-dynamics computer simulation. Calculations have been realized by using an empirical many-body potential energy function for carbon. A single-wall carbon nanotube has been considered in the simulations. It has been found that the periodic boundary condition has no effect at low temperature (1 K), however, it plays an important role even at intermediate temperature (300 K).

Atomic and electronic properties of spherical silicon clusters

We have investigated the atomic and electronic properties of spherical ideal Si N clusters ( N=5–417) using the empirical many-body potential energy function consisting of two- and three-body interactions, and by empirical tight-binding calculations, respectively. It has been found that the average interaction energy per atom decreases as the cluster size increases, and it becomes almost constant after the size N⩾275. On the other hand, the band gap shows cluster size dependent characteristics; the band gap decreases as the cluster size increases.