Structural and zero-point vibrational effects on the electric dipole moments and static dipole polarizabilities of sodium clusters

Andrés Aguado, Andrés Vega, and Luis C. Balbás

Phys. Rev. B 84, 165450 – Published 25 October 2011

Abstract

The electric dipole moments of small Na $_{n}$ clusters have been recently measured [J. Bowlan, A. Liang, and W. A. de Heer, Phys. Rev. Lett. 106, 043401 (2011)] and found to be essentially zero, a distinguishing feature of metallicity. Previous theoretical calculations fail in describing this fundamental nanoscale property. In this paper, we resolve the discrepancy by employing density functional calculations in conjunction with a highly accurate, nonlocal, van der Waals density functional. We show that knowing the correct global minimum structures is indispensable for reproducing the observed dipole moments. We also show that the dipoles are highly fluxional due to their strong coupling with zero-point vibrations, which contribute significantly to the dipole moment and polarizability values.