Rough droplet model for spherical metal clusters

N. Pavloff 1, C. Schmit 1

Physical Review B 58 (1998) 4942-4951

We study the thermally activated oscillations, or capillary waves, of a neutral metal cluster within the liquid drop model. These deformations correspond to a surface roughness which we characterize by a single parameter $\\Delta$. We derive a simple analytic approximate expression determining $\\Delta$ as a function of temperature and cluster size. We then estimate the induced effects on shell structure by means of a periodic orbit analysis and compare with recent data for shell energy of sodium clusters in the size range $50 < N < 250$. A small surface roughness $\\Delta\\simeq 0.6$ \Å~ is seen to give a reasonable account of the decrease of amplitude of the shell structure observed in experiment. Moreover -- contrary to usual Jahn-Teller type of deformations -- roughness correctly reproduces the shape of the shell energy in the domain of sizes considered in experiment.

  • 1. Division de Physique Théorique, IPN,
    Université Paris XI - Paris Sud