Mechanical deformation of atomic-scale metallic contacts: Structure and mechanisms

Abstract

We have simulated the mechanical deformation of atomic-scale metallic contacts under tensile strain using molecular dynamics and effective medium theory potentials. The evolution of the structure of the contacts and the underlying deformation mechanisms are described along with the calculated electronic conductance. Various defects such as intersecting stacking faults, local disorder, and vacancies are created during the deformation. Disordered regions act as weak spots that reduce the strength of the contacts. The disorder tends to anneal out again during the subsequent atomic rearrangements, but vacancies can be permanently present. The transition states and energies for slip mechanisms have been determined using the nudged elastic band method, and we find a size-dependent crossover from a dislocation-mediated slip to a homogeneous slip when the contact diameter becomes less than a few nm. We show that the results measured in a nanocontact experiment depend significantly on the elastic stiffness of the experimental apparatus. For a soft setup, some of the atomic rearrangements might not be detected, whereas others are amplified. ͓S0163-1829͑98͒01306-X͔

The uniaxial tensile deformation of Ni nanowire: atomic-scale computer simulations

“…5(b)) which is some similar to what happened in the gold nanowire [18,21]. However, this is not observed for Ni nanowire simulated by Sorensen et al [17]. With the further pull of the nanowire, the bond between the atoms in the necklace breaks, as shown in Fig.…”

“…In recent years, the deformation of nanowires have been studied by molecular dynamics simulations using either embodied-atom-method (EAM) [12][13][14][15] or effective-medium theory (EMT) [16,17] potentials as well as first-principles method based on the density functional theory (DFT) [18][19][20][21]. These studies focus on the correlation of the force (associated with the changes in the bonding of the nanowire) and the conductance for the metallic Au, Ni, and Na nano-contacts [17,22] and Au, Ni, Al, Na, and SiSe 2 nanowire [12,16,20,23]. The structural transformation takes place in nanoscale metallic wires under uniaxial strain [12,14,[17][18]23].…”

“…These studies focus on the correlation of the force (associated with the changes in the bonding of the nanowire) and the conductance for the metallic Au, Ni, and Na nano-contacts [17,22] and Au, Ni, Al, Na, and SiSe 2 nanowire [12,16,20,23]. The structural transformation takes place in nanoscale metallic wires under uniaxial strain [12,14,[17][18]23]. At lower strain rates, the Ni nanowire shows superplasticity [12,13], and at sufficiently high strain rates, it can transform continuously to an amorphous metal at constant temperature [13,14,23].…”

“…The Au nanowires, before breaking under tensile stress, can get as thin as one-atom chains, and as long as five suspended atoms [18,21]. Sorensen et al [17] have simulated the mechanical deformation of atomic-scale metallic contacts under tensile strain, and found that various defects such as intersecting stacking faults, local disorder, and vacancies were created during the deformation. There are many unanswered questions relating to the mechanical mechanism, especially those related to the tensile process, and are expected to be illustrated in future.…”

Theoretical study of linear monoatomic nanowires, dimer and bulk of Cu, Ag, Au, Ni, Pd and Pt

“…Most studied systems both experimentally [1][2][3][4][5][6][7] and theoretically [8][9][10][11][12][13][14][15][16] are free standing gold nanowires, which exhibit a quantized conductance at stretching and have peculiar structural properties. Unsupported and supported wires of Cu, Pd, Pt, Ag and Au have also been studied theoretically by means of ab initio and molecular dynamics methods [14], [17][18][19][20][21][22]. The influence of relativistic effects on the properties of Pd and Ag wires is analyzed in Ref.…”