0000000000602773
AUTHOR
A. Rytkönen
Effect of melting on ionization potential of sodium clusters
The effect of melting transition on the ionization potential has been studied for sodium clusters with 40, 55, 142, and 147 atoms, using ab initio and classical molecular dynamics. Classical and ab initio simulations were performed to determine the ionization potential of Na142 and Na147 for solid, partly melted, and liquid structures. The results reveal no correlation between the vertical ionization potential and the degree of surface disorder, melting, or the total energy of the cluster obtained with the ab initio method. However, in the case of 40 and 55 atom clusters, the ionization potential seems to decrease when the cluster melts.
Influence of electronic and geometric properties on melting of sodium clusters
Systematics of the melting transition for sodium clusters with 40-355 atoms has been studied with both ab initio and semiclassical molecular dynamics simulations. The melting temperatures obtained with an ab initio method for Na55 + and Na93 + correlate well with the experimental results. The semiclassically determined melting temperatures show similarities with the experimentally determined ones in the size region from 55 to 93 and near size 142, and the latent heat in the size region from 55 to 139, but not elsewhere in the size region studied. This indicates that the nonmonotonical melting behavior observed experimentally cannot be fully explained by geometrical effects. The semiclassica…
Phase coexistence in finite van der Waals systems
Phase coexistence in finite systems obeying van der Waals equation of state is studied by minimizing a model free energy function for a spherical liquid droplet and a gaseous phase around it. Phase diagrams are calculated for finite systems with a large range of sizes. According to this model, the highest temperature where a droplet and vapour can exist in equilibrium decreases as N −0.4, where N is the number of particles in the system. The model predicts higher equilibrium vapour pressures than molecular dynamics simulations.
Melting and multipole deformation of sodium clusters
Melting and multipole deformations of sodium clusters with up to 55 atoms are studied using an ab initio molecular dynamics method. The melting temperature regions for Na20, Na40, and Na 55 + are estimated. The melting temperature region determined here for Na 55 + agrees with the one determined experimentally. The dominating deformation type observed at the liquid phase for Na20 and Na40 is octupole deformation and for Na14 and Na 55 + quadrupole deformation.