13 research outputs found
An orbital-free molecular dynamics study of melting in K_20, K_55, K_92, K_142, Rb_55 and Cs_55 clusters
The melting-like transition in potasium clusters K_N, with N=20, 55, 92 and
142, is studied by using an orbital-free density-functional constant-energy
molecular dynamics simulation method, and compared to previous theoretical
results on the melting-like transition in sodium clusters of the same sizes.
Melting in potasium and sodium clusters proceeds in a similar way: a surface
melting stage develops upon heating before the homogeneous melting temperature
is reached. Premelting effects are nevertheless more important and more easily
established in potasium clusters, and the transition regions spread over
temperature intervals which are wider than in the case of sodium. For all the
sizes considered, the percentage melting temperature reduction when passing
from Na to K clusters is substantially larger than in the bulk. Once those two
materials have been compared for a number of different cluster sizes, we study
the melting-like transition in Rb_55 and Cs_55 clusters and make a comparison
with the melting behavior of Na_55 and K_55. As the atomic number increases,
the height of the specific heat peaks decreases, their width increases, and the
melting temperature decreases as in bulk melting, but in a more pronounced way.Comment: LaTeX file. 6 pages with 17 pictures. Final version with minor
change
Kinetics and equilibrium of small metallic clusters: Ab initio confinement molecular dynamics study of
The ab initio molecular dynamics (AIMD) [1]
is combined with the heuristic, successive
confinement method of surveying a potential energy surface (PES) [2],
thereby offering a framework for the simulation
study of kinetics and equilibrium properties of metallic clusters.
This approach is applied to the study of Au4, a cluster
possessing a simple but specific PES, which consists of very
shallow and deep basins and due to this presents a challenge to the
conventional AIMD methods. Among other things, the probabilities of
the transitions between isomers have been found, and on this basis,
both the time-dependent and equilibrium populations of the isomers
have been calculated for the conditions typical of the NeNePo
experiments [3] in the femtosecond pump-probe
spectroscopy