On the use of evaporation dynamics to characterize phase transitions in van der Waals clusters: investigations in aniline–(argon)n up to n=15 Original Research Article

The evaporation process in small van der Waals aniline–(argon)n clusters (with n=3, 4, 5, 8 and 15) has been investigated by molecular dynamics (MD) simulations. MD results have been compared to three statistical theories: classical RRK, the Engelking model and phase space theory (PST). The latter gives results in good agreement with the results derived from classical trajectories. The sensitivity of the average kinetic energy release to the thermodynamic phase of the product sub-cluster is put into evidence for small aniline–Arn clusters. This finding opens new perspectives on the experimental characterization of phase transitions in atomic or molecular clusters. A complete study of the final populations in the different product isomers has been performed by MD simulations and compared to an extended phase space theory (EPST) in which the densities of states of individual isomers are explicitly taken into account. Finally the use of PST in the low energy regime has allowed to address the question of the cluster temperature resulting from evaporation down to time windows in the microsecond domain of experimental interest. The thermodynamic state of the cluster is predicted to change at a critical size.