Volume 79, Number 4, August 2007
Article Number 43001
Number of page(s) 5
Section Atomic, Molecular and Optical Physics
Published online 27 July 2007
EPL, 79 (2007) 43001
DOI: 10.1209/0295-5075/79/43001

Critical analysis of negative heat capacity in nanoclusters

K. Michaelian1 and I. Santamaría-Holek2

1  Instítuto de Física, Universidad Nacional Autónoma de México - Apdo. Post. 20-364, México D.F., 01000 Mexico
2  Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México México D.F., 04510 Mexico

received 1 June 2007; accepted in final form 3 July 2007; published August 2007
published online 27 July 2007

It is shown that "negative heat capacity" in nanoclusters is an artifact of applying equilibrium thermodynamic formalism on a "small" system trapped in a metastable state differing from true thermodynamic equilibrium. Trapping occurs due to high-energy barriers separating different regions of the cluster phase space, particularly for cluster sizes near the magic numbers corresponding to closed geometrical shells. Trapping may occur in either the canonical or microcanonical ensemble, but it is unavoidable in the microcanonical and can lead to a dependence on initial conditions of the determined cluster properties.

36.40.Ei - Phase transitions in clusters.
36.40.Mr - Spectroscopy and geometrical structure of clusters.
36.40.-c - Atomic and molecular clusters.

© Europhysics Letters Association 2007