Scalar relativistic effect on lattice dimerization in metastable gold nanowire of finite length

Recent observation by Xiao et al. [L. Xiao, B. Tollberg, X. Hu, L. Wang, J. Chem. Phys. 124 (2006) 114309.] suggested substantial lattice distortion in linear gold nanowires of finite chain length up to 2 nm and remarkably they have predicted the disappearance of Peierls distortion in the infinite limit. In the present study we adopt the method of constrained relaxation search to find out the existence of true dimerization in these systems. The role of scalar relativistic effect on lattice dimerization in these nanowires has been investigated using first-principle density functional calculations at zero-order regular approximation level. It is well known that real lattice dimerization in gold nanowires are perceptible just immediately before the breakage of the wires. While exploring the role of scalar relativity, it has been observed that scalar relativity decreases the dimerization amplitude of each of the linear metastable gold nanowires compared to its non-relativistic counterpart. Another interesting observation is the greater stabilization of Au5 and Au7 in constrained relaxation search compared to that of the unconstrained relaxation scheme in relativistic method. The dramatic even-odd oscillations are observed in the values of the dimerization amplitudes, HOMO-LUMO energy gap, and second differences of wire energies. The results are very stable and consistent up to Au9.