Fragmentation phase transition in atomic clusters IV

Gross, D. H. E.; Madjet, Mohamed

doi:10.1007/s002570050488

Cited by 27 publications

(32 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Typically, the upper limits of the NF-AD stage and the lower limits of the AD-MF stage are found to be 58 ± 3 and 55 ± 3 eV, respectively, indicating the absence of a threefold coexistence. The behavior is in qualitative agreement with the typical features of the FPT predicted by Gross's group [13][14][15][16]. Actually, the experimental observations of the multistage transformation is similar to that of the melting phase transition occurring in an atomic cluster, which was proved continually to be a multistage process initiated by a "premelting" stage where the surface of a cluster melts before the core [23,24].…”

supporting

confidence: 85%

“…Unlike the macrosystem case, theoretical treatment of the fragmentation phase transition (FPT) requires a microcanonical description. In a series of theoretical works from Gross's group [13][14][15][16], the calculated caloric curve for a cluster system was found to be divided into four parts: after an initially rising, a plateau and a backbending are present before the curve rises again. The results indicate a multistage FPT corresponding to a hierarchical opening of the cluster configuration with increasing energy, which was found also related to a stepwise appearance of typical fragmentation phenomena from no fragmentation (NF) through asymmetrical dissociation (AD) and multifragmentation (MF) to complete fragmentation (CF).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Multistage transformation and charge effect during the fragmentation phase transition in atomic clusters

Qian

Chen

et al. 2013

Phys. Rev. A

View full text Add to dashboard Cite

Compared with the macrosystem case, the phase transition occurring in fragmenting cluster systems depicts a much richer story. However, most experimental observations have been restricted to an extremely partial view of this picture due to the technical limitations of a large-range scan of the energy deposited in a selected cluster system. Here, taking charge-selected C 60 3+ and C 60 4+ as model systems, we experimentally explore the fragmentation phase transition (FPT) over a large energy range and directly observe some of the most important features of the FPT, the multistage transformation, and the charge effect.

show abstract

supporting

confidence: 85%

mentioning

confidence: 99%

Multistage transformation and charge effect during the fragmentation phase transition in atomic clusters

Qian

Chen

et al. 2013

Phys. Rev. A

View full text Add to dashboard Cite

show abstract

“…In particular, the previous extended canonical MC algorithms can be useful to study Potts models with many spin states and higher dimensions, as the cases shown in FIG.6, where we illustrate the caloric curves derived from MC simulations by using the extended SW algorithm for q = 10, d = (2,3,4), and a fixed number of lattice sites N = L d = 4096. The comparative study case with the Wang-Landau method shown in the inset panel allows us to verify that the agreement between these methods is more significant with the increasing of N .…”

Section: Resultsmentioning

confidence: 99%

“…could be extended by using a minimal, but crucial modification in their schemes to account for the existence of an anomalous regime with negative heat capacities C < 0 [1,2,3,4,5,6]. This fact avoids the incidence of the so-called super-critical slowing down, a dynamical anomaly that significantly affects the efficiency of large-scale canonical MC simulations [7].…”

Section: Introductionmentioning

confidence: 99%

Extending canonical Monte Carlo methods

Velázquez

Curilef

2010

J. Stat. Mech.

View full text Add to dashboard Cite

In this work, we discuss the implications of a recently obtained equilibrium fluctuation-dissipation relation on the extension of the available Monte Carlo methods based on the consideration of the Gibbs canonical ensemble to account for the existence of an anomalous regime with negative heat capacities C < 0. The resulting framework appears as a suitable generalization of the methodology associated with the so-called dynamical ensemble, which is applied to the extension of two well-known Monte Carlo methods: the Metropolis importance sample and the Swendsen-Wang clusters algorithm. These Monte Carlo algorithms are employed to study the anomalous thermodynamic behavior of the Potts models with many spin states q defined on a d-dimensional hypercubic lattice with periodic boundary conditions, which successfully reduce the exponential divergence of decorrelation time τ with the increase of the system size N to a weak power-law divergence τ ∝ N α with α ≈ 0.2 for the particular case of the 2D 10-state Potts model.

show abstract

“…Conversely, for short range interactions [3] the backbending is a surface effect which should disappear at the thermodynamical limit. This is the case for the microcanonical model of fragmentation of atomic clusters [13] and for the lattice gas model with fluctuating volume [14] . The interphase surface entropy goes to zero as N → ∞ in these models leading to a linear increase of the entropy in agreement with the canonical predictions.…”

mentioning

confidence: 99%

Failure of thermodynamics near a phase transition

Gulminelli

Chomaz

2002

Phys. Rev. E

View full text Add to dashboard Cite

We investigate the relation between various statistical ensembles of finite systems. If ensembles differ at the level of fluctuations of the order parameter, we show that the equations of states can present major differences. A sufficient condition for this inequivalence to survive at the thermodynamical limit is worked out. If energy consists in a kinetic and a potential part, the microcanonical ensemble does not converge towards the canonical ensemble when the partial heat capacities per particle fulfill the relation c −1PACS numbers: 05.20. Gg, 64.10.+h, 05.70.Fh In most textbooks the equivalence between the different statistical ensembles is demonstrated at the thermodynamical limit through the Van Hove theorem [1]. Indeed ensembles differ at the level of fluctuations which are generally believed to induce small corrections in finite systems and to become negligeable at the limit of infinite systems.In this paper we will show that this might not be always the case. For finite systems, two ensembles which put different constraints on the fluctuations of the order parameter lead to qualitatively different equations of states close to a first order phase transition. As an example the microcanonical heat capacity may diverge to become negative while the canonical one remains always positive and finite [2,3]. Such inequivalences may survive at the thermodynamical limit for systems involving long range forces [4,5]. Looking at the general properties of the order parameter distribution a sufficient condition for this behavior to show up can be explitely worked out.Let us first concentrate on finite systems. For simplicity we will consider the microcanonical and the canonical ensemble characterized by the energy E and the temperature β −1 respectively, but our discussion is valid for any couple of conjugated extensive and intensive variables.The microcanonical ensemble is characterized by the level density W (E) and the entropy S = log W .The caloric curve is then T −1 = ∂ E S. The canonical partition sum is the Laplace transform of W : Z β = dEW exp(−βE). In this article we will assume that the partition sum converges; this is not always the case [6] and indeed the impossibility to normalize the distribution W exp(−βE) is already a known case of ensemble inequivalence.In finite systems, the canonical ensemble differs from the microcanonical one since it does not correspond to a unique energy but to a distribution P β (E) = exp(S(E) − βE − log Z β ). If P β has a single maximum the average energy E β = −∂ β ln Z β can also be computed using a saddle point approximation around the most probable energy E βwith g β (x) = c 0 +c 3 x 3 +c 4 x 4 +. . . . If P β is symmetric,The definition of saddle impliesmeaning that the microcanonical caloric curve T (E) exactly coincides with the canonical one β −1 ( E ). However in a finite system the distribution may be not symmetric so that the two curves can be shifted :.. withg β the series of the odd terms of g β . However, the shift δ is in most cases small so that when P β h...

show abstract

Fragmentation phase transition in atomic clusters IV

Cited by 27 publications

References 18 publications

Multistage transformation and charge effect during the fragmentation phase transition in atomic clusters

Multistage transformation and charge effect during the fragmentation phase transition in atomic clusters

Extending canonical Monte Carlo methods

Failure of thermodynamics near a phase transition

Contact Info

Product

Resources

About