Effect of Impurities in the Large Au-Au Distances in Gold Nanowires

Abstract

Experimentally obtained atomically thin gold nanowires have presented exceedingly large Au-Au interatomic distances before they break. Since no theoretical calculations of pure gold nanowires have been able to produce such large distances, we have investigated, through ab initio calculations, how impurities could affect them. We have studied the effect of H, B, C, N, O, and S impurities on the nanowire electronic and structural properties, in particular how they affect the maximum Au-Au bond length. We find that the most likely candidates to explain the distances in the range of 3.6 A and 4.8 A are H and S impurity atoms, respectively.

Computational Tools to Study and Predict the Long-Term Stability of Nanowires.

“…This choice was made because in the literature we found first principles calculations, similar to those performed here, where the H and C were positioned at a similar place, as well as between the Au 2 and Au 3 atoms, with similar results (Novaes et al, 2003;Skorodumova et al, 2007). As it will be found below, the present results agree with those where the impurity was located at another sites of the chain.…”

“…The rupture force will be considered to be the value of the force F z where it presents a maximum at long elongations, being the force defined in Eq. 8 (da Silva et al, 2004;Jelínek et al, 2008;Novaes et al, 2003;Novaes et al, 2006;Rubio-Bollinger et al, 2001;Vélez et al, 2005;Vélez et al, 2008). Accordingly, we refer in the following to the "at rupture" state as that where the coordinates of the atoms are such that 0 z Fz ∂ ∂Δ = (maximum force).…”

“…The use of ab-initio quantum methods to study the stability of monatomic metallic nanowires is usually performed using two different methodologies. One of these procedures involves stretching the nanowire in steps of a certain elongation, minimizing the energy of the system at each step, until the breakage of the nanowire is achieved (Bahn et al, 2002;da Silva et al, 2004;De Maria & Springborg, 2000;Häkkinen et al, 2000;Nakamura et al, 1999;Nakamura et al, 2001;Novaes et al, 2003;Okamoto & Takayanagi, 1999;Rubio-Bollinger et al, 2001;Sánchez-Portal et al, 1999;Skorodumova & Simak, 2003). This method has been successfully used to, for example, predict the pulling force necessary for breaking the nanowire (da Silva et al, 2004;Nakamura et al, 1999;Novaes et al, 2003;Rubio-Bollinger et al, 2001).…”

“…One of these procedures involves stretching the nanowire in steps of a certain elongation, minimizing the energy of the system at each step, until the breakage of the nanowire is achieved (Bahn et al, 2002;da Silva et al, 2004;De Maria & Springborg, 2000;Häkkinen et al, 2000;Nakamura et al, 1999;Nakamura et al, 2001;Novaes et al, 2003;Okamoto & Takayanagi, 1999;Rubio-Bollinger et al, 2001;Sánchez-Portal et al, 1999;Skorodumova & Simak, 2003). This method has been successfully used to, for example, predict the pulling force necessary for breaking the nanowire (da Silva et al, 2004;Nakamura et al, 1999;Novaes et al, 2003;Rubio-Bollinger et al, 2001). An alternative procedure, and more costly from a computational point of view, consists in performing Ab-initio Molecular Dynamics (AIMD), which has been employed to obtain a detailed description of the elongation process of pure gold nanowires (Hobi et al, 2008;Torres et al, 1999), and gold NWs in the presence of organic molecules (Krüger et al, 2002), or light weight elements as contaminants (Hobi et al, 2008;Legoas et al, 2004).…”

“…Subsequently, the influence of carbon was explored using the same computational methodology (Skorodumova et al, 2007;Skorodumova & Simak, 2004), also finding that carbon can enhance the stability of linear gold chains yielding large interatomic distances. Novaes et al (Novaes et al, 2003) studied through ab-initio calculations the effect of H, B, C, N, O and S impurities on a gold nanowire electronic and structural properties. The authors find that the most likely candidates to explain the distances in the range of 3.6 Å and 4.8 Å are H and S impurity atoms, respectively.…”