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Title

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

AuthorsPérez de Tudela, Ricardo ; Márquez-Mijares, Maykel ; González-Lezana, Tomás ; Roncero, Octavio ; Miret-Artés, Salvador ; Delgado Barrio, Gerardo ; Villarreal, Pablo
KeywordsArgon
Liquid-vapour transformations
Molecular clusters
Molecular configurations
Monte Carlo methods
Quantum theory
Rotational-vibrational states
Specific heat
Issue Date23-Jun-2010
PublisherAmerican Institute of Physics
CitationThe journal of chemical physics, 132 (24): 244303 (2010)
AbstractThe 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.
Description10 pags. ; 7 figs.
Publisher version (URL)http://dx.doi.org/10.1063/1.3445773
URIhttp://hdl.handle.net/10261/28203
DOI10.1063/1.3445773
ISSN0021-9606
Appears in Collections:(CFMAC-IFF) Artículos
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