Ab initiostudy of helical silver single-wall nanotubes and nanowires

Abstract

We report results for the electronic structures of extended silver single-wall nanotubes ͑AgSWNTs͒ within a first-principles, all-electron self-consistent local density functional approach adapted for helical symmetry. We carried out calculations on twenty-one different AgSWNTs ranging in radii from approximately 1.3 Å to 3.6 Å. AgSWNTs with radii greater than 2.2 Å were also calculated with a silver atomic chain inserted along the nanotube axis; we refer to these composite structures as silver nanowires ͑AgNWs͒. Energetic trends for the AgSWNTs are not as predictable as expected. For example, the total energy does not necessarily decrease monotonically as nanotube radius increases, as is the case for single-wall carbon nanotubes. The conductivity of these AgSWNTs and AgNWs is also addressed. Similar to the case for helical gold nanowires, the number of conduction channels in the AgSWNTs does not always correspond to the number of atom rows comprising the nanotube. However, for all AgNWs considered, the additional silver atomic chain placed along the tube's axis results in one additional conduction channel.

Density Functional Study of the Structure, Stability and Oxygen Reduction Activity of Ultrathin Platinum Nanowires

“…Furthermore, as compared to the DOS of platinum, there are quite a few conspicuous peaks in the DOS of all NTs and NWs. Notable ones, for instance, include two peaks at −3.7 and −0.9 eV in DOS of the (6,6)SWPtNT, two peaks at −1.8 and −0.7 eV in the (13,13) SWPtNT and three peaks at −3.8, −1.8 and −0.5 eV in DOS of the (6,6)@(13,13) DWPtNT. Figure 3 further indicates that the position of the Fermi level is pushed up as the number of platinum row strands in NTs increases, from −5.00 eV in the (6,6) SWPtNT to −4.51 eV in the (13,13) SWPtNT and −3.68 eV in the (6,6)@ (13,13) DWPtNT.…”

“…Notable ones, for instance, include two peaks at −3.7 and −0.9 eV in DOS of the (6,6)SWPtNT, two peaks at −1.8 and −0.7 eV in the (13,13) SWPtNT and three peaks at −3.8, −1.8 and −0.5 eV in DOS of the (6,6)@(13,13) DWPtNT. Figure 3 further indicates that the position of the Fermi level is pushed up as the number of platinum row strands in NTs increases, from −5.00 eV in the (6,6) SWPtNT to −4.51 eV in the (13,13) SWPtNT and −3.68 eV in the (6,6)@ (13,13) DWPtNT. The distribution of energy bands around the Fermi level also gets more crowded as the number of strands in the NT increases and the number of conduction bands increases from four in the (6,6) to five in the (13,13) SWPtNT, and to nine in the (6,6)@(13,13) DWPtNT.…”

“…Both tubes have larger diameters than in the relaxed hollow (6,6)@(13,13) NT where the outer and inner tube have an average widths of 10.75 Å and 5.47 Å, respectively. The outer (13,13) tube of the relaxed (6,6)@(13,13) NW is formed of alternating rows of platinum atoms in the shape of irregular pentagons. The inner (6,6) tube is also slightly deformed and platinum atoms form different irregular hexagons along the tubes axes.…”

“…Structure.-The energies of the relaxed (6,6) and (6,6)@ (13,13) NWs are calculated as −5.09 eV and −5.51 eV per atom while the energies of the (6,6) and (6,6)@(13,13) NTs are −4.97 eV and −5.44 eV per atom. Both NWs are thus thermodynamically more stable than the corresponding hollow NTs due to the favorable interactions between the platinum atoms of the inner chain and the outer tube.…”

Electron transfer across a conducting nanowire (nanotube)/electrolyte solution interface

“…Several attempts were made to describe the structure and electronic properties of gold nanowires [14,15], and of silver and carbon single wall nanotubes (SWNTs) [16,17] using quantum chemical calculations, mostly at the density functional theory (DFT) level. DFT was also employed to study the adsorption behaviour of oxygen and CO molecules at single gold chains [18], as well as some organic species attached to monoatomic Au wires [19,20].…”