Typeset using REVTEX 1

Molecular dynamics computer simulations which employ the embedded-atom potential show that nanowires of gold exist as multishelled structures. We simulate double-walled gold nanowires and calculate the capacitance of a finite nanometer-size cylindrical capacitor. For the sizes for which multishelled nanowires appear in simulations we find the capacitances below one attofarad. 1 Finite-size systems of atomic scale dimensions have attracted great attention. Interest is focused on fundamental aspects, as well as on applications. The remarkable physical properties of nanostructures allow one to design nano-scale electrical and mechanical devices. The continuing miniaturization of engineering devices leads to a technological revolution. Research on the properties of cylindrical nanostructures of various materials, ie., nanowires, has been especially active field. Multishelled nanostructures were produced for carbon clusters and wires [1,2], as well as for wires of W S 2 , MoS 2 , and NiCl 2 [3]. Gold nanowires are fabricated by Scanning Tunneling Microscopy (STM) [4,5] and electron-beam litography [6]. In recent Molecular Dynamics (MD) computer simulation multishelled cylindrical nanostructures of gold were obtained [7]. Wires with radii around a nanometer and a length/diameter ratio between 1 and 3 were studied. It was found that multiwalled structures exist for longer of these nanowires, i.e., for a length/diameter ratio of 2 and 3. The formation of shells was also found in a jellium model calculation for finite sodium nanowires [8]. This was confirmed by the conductance measurements [9]. We simulate here double-walled gold nanowires and study the capacitance for this geometry. It is well known that an application of a many-body potential is necessary for accurate description of metallic bonding by the MD simulation method [10]. We used here (as in Ref. [7]) an embedded-atom potential for gold which produces a good agreement with available experimental results for bulk, surfaces, and nanoparticles [11]. A time step of 7.14 × 10 −15 s was employed in simulation. The temperature was controlled by rescaling the particle velocities. We started from an ideal fcc (111) structure at T = 0 K, and included in the cylindrical MD box all particles whose distance from the nanowire axis was smaller than 1.2 nm. The length of the sample of 689 atoms was 6 layers. We also studied a nanowire of 9 layers and 1032 particles. The samples were first relaxed, then annealed and quenched. To prevent melting and collapse into a drop, instead of usual heating to ∼ 1000 K …