A plane-wave pseudopotential description of charged clusters

Abstract

One of the most efficient approaches in computational cluster physics uses a plane-wave basis set and pseudopotentials to describe electron–ion interactions. This method – where the clusters are placed inside supercells – is restricted in its usual form to neutral systems because of the long-range interaction between a charged cluster and its periodic images. To eliminate this restriction, we propose to shield each charged cluster with a spherical shell having a symmetric charge that neutralizes the supercell. Furthermore, the shell is placed in such a way that it cancels the electric dipole of the charged cluster. We present relaxed geometries and cohesive energies of Na N +, N=2-9 and 21, obtained with Langevin quantum molecular dynamics. Our local density approximation structures are very similar to those found in other first principles calculations. Vertical and adiabatic ionization energies of Na N, N=2,?3,?6, and 8 are displayed. We also show results for Na 8 2+, Na 5 - and Na 7 -