A new Monte Carlo method for getting the density of states of atomic cluster systems

A novel Monte Carlo flat histogram algorithm is proposed to get the classical density of states in terms of the potential energy, g ( E p ), for systems with continuous variables such as atomic clusters. It aims at avoiding the long iterative process of the Wang-Landau method and controlling careful...

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Bibliographic Details
Published in:The Journal of chemical physics 2011-10, Vol.135 (14), p.144109-144109-15
Main Authors: Soudan, J.-M., Basire, M., Mestdagh, J.-M., Angelié, C.
Format: Article
Language:English
Subjects:
Chemical Sciences
or physical chemistry
Theoretical and
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Summary:A novel Monte Carlo flat histogram algorithm is proposed to get the classical density of states in terms of the potential energy, g ( E p ), for systems with continuous variables such as atomic clusters. It aims at avoiding the long iterative process of the Wang-Landau method and controlling carefully the convergence, but keeping the ability to overcome energy barriers. Our algorithm is based on a preliminary mapping in a series of points (called a σ-mapping), obtained by a two-parameter local probing of g ( E p ), and it converges in only two subsequent reweighting iterations on large intervals. The method is illustrated on the model system of a 432 atom cluster bound by a Rydberg type potential. Convergence properties are first examined in detail, particularly in the phase transition zone. We get g ( E p ) varying by a factor 10 3700 over the energy range [0.01 < E p < 6000 eV], covered by only eight overlapping intervals. Canonical quantities are derived, such as the internal energy U ( T ) and the heat capacity C V ( T ). This reveals the solid to liquid phase transition, lying in our conditions at the triple point. This phase transition is further studied by computing a Lindemann-Berry index, the atomic cluster density n( r ), and the pressure, demonstrating the progressive surface melting at this triple point. Some limited results are also given for 1224 and 4044 atom clusters.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.3647333