(559d) Study of Geometries and Electronic Properties of Pd and Pd-Ni Alloy Chains on Single-Walled Carbon Nanotubes

Earlier experiments have shown the possibility of forming suspended stable single atomic Pd or Ni chains on SWNTs.[1,2] Transmission electron microscopy studies reveal the quasi-continuous formation of Pd and Ni coating on suspended carbon nanotubes.[3] In this paper, we investigate the binding and geometries of Pd and Pd-Ni atomic chains on two types of single-walled carbon nanotubes (SWNTs). Pd and its Ni alloy are commonly employed in hydrogen reactions. Pd/Ni alloys are also used in hydrogen sensors to improve reliability, speed of response, and selectivity. The calculations were performed using pseudo-potential (PP) plane wave method within Density Functional Theory (DFT) and the Generalized Gradient Approximation (GGA) of Perdew and Wang, known as PW91. Two configurations of chains were studied, namely straight chains and zigzag chains. The cohesive energy calculations on free standing infinite Pd and Pd-Ni monatomic chains shows stable formation of small angle zigzag chains, and a meta-stable formation of wide angle zigzag chains. We will further explore the effect of chains formation of adsorbates and investigate the chains on SWNTs. We also explore the electronic properties of Pd, Pd-Ni functionalized SWNTs and their possible contributions as novel sensing and catalytic materials. Calculations for binding energies, charge transfer, density of states and band gap will be presented for these different systems.

References

[1]. H. Ohnishi, Y. Kondo, and K. Takayanagi, Nature 395, 780 (1998).

[2]. A. I. Yanson, G. R. Bollinger, H. E. van den Brom, N. Agraït, and J. M. van Ruitenbeek, Nature 395, 783 (1998).

[3]. Y. Zhang, N. W. Franklin, R. J. Chen, and H. Dai, Chem. Phys. Lett. 331, 35 (2000).