The mechanical properties of ultrathin germanium nanowires are investigated: the mechanical properties of the nanowires are severely reduced when temperature increases.

The CO oxidation mechanism catalyzed by ultrathin helical palladium nanowires (PdNW) was investigated by density functional theory (DFT) calculation. The helical PdNW structure was constructed on the basis of the simulated annealing basin-hopping (SABH) method with the tight-binding potential and the penalty method in our previous studies (J. Mater. Chem., 2012, 22, 20319). The low-lying adsorption configurations as well as the adsorption energies for O2 and CO molecules on different PdNW adsorption sites were obtained by DFT calculation. The most stable adsorption configurations for the Langmuir-Hinshelwood (LH) mechanism processes were considered for investigating the CO oxidation mechanism. The nudged elastic band (NEB) method was adopted to obtain the transition state configuration and the minimum energy pathways (MEPs).

Employing the basin-hopping method with the Stillinger–Weber potential and penalty function, four germanium nanowires with the most stable energies were obtained at cross-section radii of 1.8 Å, 2.0 Å, 2.4 Å, and 2.9 Å, respectively. Because the coordination numbers and orbital hybridizations of Ge atoms in these nanostructures are different from bulk Ge, their density of states (DOS) profiles are distinctly different from that of bulk. Besides, the discrepancies of DOS among these nanowires arising from different electron density overlaps induce the different Coulomb interactions. Furthermore, the enhanced Coulomb interaction and the quantum confinement in germanium nanowires cause the original p-orbitals below Fermi-level shift up to cross the Fermi-level, which leads Ge nanowires to be conductors.