Thermal expansion in small metal clusters and its impact on the electric polarizability

Abstract

The thermal expansion coefficients of ${\mathrm{Na}}_N$ clusters with $8\le N\le 40$ and ${\mathrm{Al}}_7$, ${\mathrm{Al}}_{13}^{-}$ and ${\mathrm{Al}}_{14}^{-}$ are obtained from {\it ab initio} Born-Oppenheimer LDA molecular dynamics. Thermal expansion of small metal clusters is considerably larger than that in the bulk and size-dependent. We demonstrate that the average static electric dipole polarizability of Na clusters depends linearly on the mean interatomic distance and only to a minor extent on the detailed ionic configuration when the overall shape of the electron density is enforced by electronic shell effects. The polarizability is thus a sensitive indicator for thermal expansion. We show that taking this effect into account brings theoretical and experimental polarizabilities into quantitative agreement.

4 pages, 2 figures, one table. Accepted for publication in Physical Review Letters. References 10 and 23 updated

References in corpus (1)

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