Mechanochemistry in Cu nanowires: N andN2enhancing the atomic chain formation

Abstract

We show using ab initio total-energy calculations based on density-functional theory how H, B, C, N, O, S, and N 2 impurities incorporated to thin copper nanowires could affect their mechanical properties and electronic structure. An interesting mechanochemical effect arises from the insertion of N and N 2 in the linear atomic chain. These impurities form not only stable but also very strong p-d bonds, in such a way that they can extract atoms from a stable tip enhancing the atomic chain suggesting the possibility to pull a string of copper atoms through the production of copper nanowires in nitrogen atmospheres.

Effect of light impurities on the electronic structure of copper nanowires

“…While Cu-Cu bonds tend to be in the range of around 2.2 to 2.7Å, the large distances provided by the effect of the atomic impurities are 3.47/3.54Å for H, 3.91/3.90Å for B, 3.66/3.68Å for C, 3.62/3.62Å for N, 3.60/3.62Å for O, and the largest of all 4.32/4.33Å for S, respectively, for LDA/GGA XC calculations. 34 These results correlate well with the order of the covalent radii of these elements, and HRTEM images similar to the ones produced in the case of Au NWs could verify these values. Figure 7 displays the PDOS of the LAC doped with N 2 impurity where we observed also the mechanochemical effect attributed to the incorporation of nitrogen.…”

“…This becomes clear when we observe two distinct situations for each p electron in peaks ii and iii; they are perpendicular orbitals. Figure 4 displays the PDOS for the Cu LAC with N. In this distinct case, we observe the mechanochemical effect which causes the reconstruction of tips, enhancing the atomic chain size, resulting in a longer LAC, 34 clearly evidencing the strong bond formed between copper and nitrogen in this low coordination situation. This case shows two s electrons in peak i and three p electrons respectively for peaks ii, iii, and iv.…”

“…Among these impurities, N and N 2 stood out as peculiar cases because their bonds with LAC atoms are so stable and strong that they could be used to pull atoms from the tips, enhancing the atomic chain and revealing an interesting mechanochemical effect. 34 From the configuration before the rupture, the calculated electronic structure was used to understand the nature of bonds between copper and impurities in this extreme situation, far from copper in bulk. In Figs from left to right, considering just occupied states up to the Fermi level.…”

“…The mechanochemical relation between thiolates and gold which allow one to pull a string of gold atoms from a gold surface 31 was also investigated in the case of copper, 32,33 as well as the incorporation of N and N 2 into copper LACs that enhance their strength, causing the rearrangement of their tips and producing larger LACs. 34 A detailed investigation of the interaction of atomic and molecular light impurities with nanocontacts and nanowires is essential for both fundamental and applied perspectives; therefore in this work we study this very important problem, that has been addressed in the case of gold nanowires, with very interesting results and consequences: [10][11][12][13]15,16 how bonds are formed between copper and light impurities in these extremely low-coordination Cu LACs. This is a very interesting question because in short LACs, one impurity causes a great deal of change in the electronic properties of the system, and these effects can be observed in the enhancement of bond lengths by HRTEM experiments.…”

Influence of one CO molecule on structural and electronic properties of monatomic Cu chain

“…The addition of the impurity remarkably modifies both the mechanical stability and electronic properties of the clean nanowires. In addition, the formation processes of the thin Cu nanowires in the presence of the impurities (H, B, C, N, O, S or N 2 ) have been simulated by Amorim et al [26] using ab initio total energy calculations. They have shown that the N and N 2 contaminated Cu nanowires exhibit very strong p-d bonds, in such a way Cu atoms can be extracted from a stable tip and join into the wire upon stretching.…”