Decay of charged stabilized jellium clusters

Abstract

The stabilized jellium model is a simple modification of the jellium model, which more realistically describes simple metals of high density, such as Al, Ga, Pb, etc. We analyzed the fragmentation processes of charged spherical A1 clusters in the framework of the stabilized jellium model. Kohn-Sham calculations of the parents and daughters, using the local density approximation, have been made. We evaluated the dissociation energies of AIL, AI;?, and Al,, with N = 1-30 atoms, in all possible decay channels. We discuss the most favorable decay channels, which are ruled by the shell structure (magic numbers of valence electrons in the parents and the daughters) oscillations around an average trend given by a liquid drop model. We compare our calculations with others and with the available experimental data. 0 1995 John Wiley & Sons, Inc. . Introductionn previous works, the surface and cohesive I properties of bulk-stabilized jellium and the energetics of small stabilized jellium clusters were studied [l-41. In this work, we studied the decay of charged aluminum clusters containing up to 30 atoms within the stabilized jellium model. The stabilized jellium model retains the simplicity and universality of the jellium model, widely used in cluster physics. Both are simple in the sense that the ions are replaced by a continuous charge background and universal in the sense that the only input parameters are the density parameter r , (the ionic charge density is n = 3/47~r,', for disInternational Journal of Quantum Chemistry, Vol. 56, 239-246 (1995) 9 1995 John Wiley 8, Sons, Inc. tances smaller than the cluster radius R = r, N,f'3, with N , the number of valence electrons of the neutral cluster) and the valence ; . The stabilized jellium model cures some deficiencies of the jellium model: unrealistic binding energies at all densities, unrealistic bulk moduli at low densities, and unrealistic surface energies at high densities. All these results follow from the instability of jellium at densities different from r , = 4.00 bohr. In the stabilized jellium model, which is clearly more realistic than is jellium for A1 (which has r , = 2.07 bohr and z = 3), we add to the electrostatic potential inside the cluster a constant potential, different for each metal, and constructed in order to have stability of the bulk metal at the observed density.

The two-centre shell model for the fission of metallic clusters

“…It is known that the LDM gives a good average of the Kohn-Sham energies of spherical jellium clusters, even for very small clusters, neutral [37] as well as charged [25]. If the spherical symmetry is broken, a better agreement of the LDM with quantal results is expected, since the shell fluctuations are then less pronounced.…”

“…This is therefore an extension of our work of [25], where we have used a pure energetic criterium to get information about cluster stability (we have calculated the heats of reaction, i.e., the energy difference between the mother and the daughter clusters).…”

Volume shift and charge instability of simple-metal clusters

“…In our present work the volume is allowed to change while the system keeps a spherical shape. More charge is needed to blow-up the volume than to deform the shape and fragment the cluster [19]. Fig.…”

Self‐expansion and compression of charged clusters of stabilized jellium

“…It has been used in Ref. [4,131 without any self-expansion or compression effects. We stress that the LDM formula (2.2) is only justified when the charge v is small in comparison with the total number of electrons N = No + v.…”