Finite gold nanowires containing less than 1000 atoms are studied using the molecular dynamics simulation method and embedded atom potential. Nanowires with the face-centered cubic structure and the (111) oriented cross-section are prepared at T=0 K. After annealing and quenching the structure and vibrational properties of nanowires are studied at room temperature. Several of these nanowires form multi-walled structures of lasting stability. They consist of concentrical cylindrical sheets and resemble multi-walled carbon nanotubes. Vibrations are investigated by diagonalization of the dynamical matrix. It was found that several percents of vibrational modes are unstable because of uncompleted restructuring of initial fcc nanowires.Comment: 4 figures in gif forma

The temperature dependence of structural properties for infinitely long gold nanowires is studied. The molecular dynamics simulation method and the embedded-atom potential are used. The wires constructed at T = 0 K with a face-centered cubic structure and oriented along the (111), (110), and (100) directions are investigated. It was found that multiwalled structures form in all these nanowires. The coaxial cylindrical shells are the most pronounced and well-formed for an initial fcc(111) orientation. The shells stabilize with increasing temperature above 300 K. All nanowires melt at T < 1100 K, i.e., well below the bulk melting temperature.Keywords: A. nanostructures, A. metals, A. surfaces and interfaces, B. nanofabrications, D. phase transitions.Typeset using REVT E X 1 Metallic nanowires are important for applications and for understanding of fundamental properties of materials at nanoscales. Over the past several years investigations on metallic nanowires were devoted mainly to the properties of cylindrical junctions formed between a metallic tip and a metallic substrate [1]. Gold nanostructures whose diameter and length are about 1 nm were recently formed in a scanning tunneling microscope and studied by a highresolution electron microscope [2,3]. Unusual vertical rows of gold atoms were observed. Therefore, it is important to study the internal structure of gold nanowires. Computer simulations are suitable for these investigations.An important topic in the cluster science is the melting of nanoparticles [4][5][6]. Experimental, theoretical, and computer simulation studies have shown that the melting temperature depends on the cluster size. These studies suggest the dependence of the form:where T m is the melting temperature for the spherical nanoparticle of radius R, T b is the bulk melting temperature, and c is a constant. In recent studies deviations from this law for small sizes are found [5,6]. Melting of clusters, i.e., spherical nanoparticles, was the subject of several recent experiments [6]. In contrast, melting of nanowires was not studied experimentally. The exception is an early work on mercury filaments with diameters between 2 and 10 nm [7]. In this experiment a decrease in the melting temperature was detected from the resistance measurements. It is well known that the presence of geometric (i.e., atomic) and electronic shells determines various properties of clusters [6]. Electronic shells in finite sodium nanowires were recently found in a jellium model calculation [8]. These shells were also observed in the conductance measurements [9]. The Molecular Dynamics (MD) simulation has shown an existence of multishelled finite gold nanowires at room temperature [10]. The cylindrical shells obtained in this simulation resemble geometric shells in clusters. Infinite wires with periodic boundary conditions along the wire axes are more often studied by MD simulations. For example, structures of ultra-thin infinite Pb and Al nanowires at T = 0 K were studied by MD simulation [11]. In comparison...

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The room temperature structure of aluminum, copper and gold infinite nanowires is studied. The molecular dynamics simulation method and the same type of the embedded atom potentials made by Voter and coworkers are used. It was found that multi-shelled and various filled metallic nanowires exist depending on the metal and the initial configuration. The results were compared with previous simulations for gold nanowires using different type of the potential.

We study the microscopic aspects of the phase separation connected with the sharp edges recently observed on the equilibrium crystal shape of lead, about twenty degrees below the bulk melting temperature. We present molecular-dynamics simulations based on a manybody interatomic potential. The high-temperature orientational phase separation can be viewed as a faceting induced by anisotropy of surface melting and should occur quite universally for vicinals of nonmelting crystal surfaces.

Finite magnesium oxide nanotubes are investigated. Stacks of four parallel squares, hexagons, octagons, and decagons are constructed and studied by the pseudopotential density functional theory within the local-density approximation. Optimized structures are slightly distorted stacks of polygons. These clusters are insulators and the band gap of 8.5 eV is constant over an investigated range of the diameters of stacked polygonal rings. Using the L"owdin population analysis a charge transfer towards the oxygen atoms is estimated as 1.4, which indicates that the mixed ionocovalent bonding exists in investigated MgO nanotubes

Deformation properties of multi-wall gold nanowires under compressive loading are studied. Nanowires are simulated using a realistic many-body potential. Simulations start from cylindrical fcc (111) structures at T = 0 K. After annealing cycles axial compression is applied on multi-shell nanowires for a number of radii and lengths at T = 300 K. Several types of deformation are found, such as large buckling distortions and progressive crushing. Compressed nanowires are found to recover their initial lengths and radii even after severe structural deformations. However, in contrast to carbon nanotubes irreversible local atomic rearrangements occur even under small compressions.

In the process of molecular dynamics simulation studies of gold nanowires an interesting structure is discovered. This is a finite double-wall nanowire with a large empty core similar to single-wall and double-wall carbon nanotubes. The structure of the 16−10 gold nanotube is studied at the room temperature. An investigation of the high-temperature stability has also been carried out. An unusual inward evaporation of atoms from cylindrical liquid walls is found at T ≥ 1200 K.