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Open Access item A path-integral Monte Carlo study of a small cluster: The Ar trimer

Authors:Pérez de Tudela, Ricardo
Márquez-Mijares, Maykel
González Lezana, Tomás
Roncero, Octavio
Miret-Artés, Salvador
Delgado Barrio, Gerardo
Villarreal, Pablo
Keywords:Argon, Liquid-vapour transformations, Molecular clusters, Molecular configurations, Monte Carlo methods, Quantum theory, Rotational-vibrational states, Specific heat
Issue Date:23-Jun-2010
Publisher:American Institute of Physics
Citation:The journal of chemical physics, 132 (24): 244303 (2010)
Abstract:The Ar3 system has been studied between T = 0 K and T = 40 K by means of a path-integral Monte Carlo (PIMC) method. The behavior of the average energy in terms of the temperature has been explained by comparison with results obtained with the thermal averaged rovibrational spectra estimated via: (i) a quantum mechanical method based on distributed Gaussian functions for the interparticle distances and (ii) an analytical model which precisely accounts for the participation of the dissociative continua Ar2+Ar and Ar+Ar+Ar. Beyond T ∼ 20 K, the system explores floppier configurations than the rigid equilateral geometry, as linear and Ar–Ar2-like arrangements, and fragmentates around T ∼ 40 K. A careful investigation of the specific heat in terms of a confining radius in the PIMC calculation seems to discard a proper phase transition as in larger clusters, in apparent contradiction with previous reports of precise values for a liquid-gas transition. The onset of this noticeable change in the dynamics of the trimer occurs, however, at a remarkably low value of the temperature in comparison with Arn systems formed with more Ar atoms. Quantum mechanical effects are found of relevance at T ≤ 15 K, with both energies and radial distributions obtained with a quantum PIMC deviating from the corresponding classical results, thus precluding exclusively classical approaches for a precise description of the system at this low temperature range.
Description:10 pags. ; 7 figs.
Publisher version (URL):http://dx.doi.org/10.1063/1.3445773
Appears in Collections:(CFMAC-IFF) Artículos

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