Pressure dependent study of the solid-solid phase change in 38-atom Lennard-Jones cluster

Abstract

Phase change phenomena in clusters are often modeled by augmenting physical interaction potentials with an external constraining potential to handle evaporation processes in finite temperature simulations. These external constraining potentials exert a pressure on the cluster. The influence of this constraining pressure on phase change phenomena in 38-atom Lennard-Jones clusters is investigated, and it is demonstrated that modest changes in the parameters of the constraining potential can lead to an order of magnitude change in the constraining pressure. At sufficiently high pressures the solid to solidlike phase change region in the 38-atom Lennard-Jones cluster is completely eliminated.

Thermodynamics and equilibrium structure of Ne38 cluster: Quantum mechanics versus classical

“…Nevertheless, the confining radius of R c = 2.65 σ LJ , which is a minimal requirement for a classical cluster, is no longer satisfactory for the quantum Ne 38 cluster, whence our decision to employ the significantly larger Lee, Barker, and Abraham value of R c = 3.612 σ LJ appears justified, although not computationally optimal in the sense of Ref. [29]. We have employed exactly the same parallel tempering Each of the six curves has been computed by collecting averages for successive groups of 50 million passes.…”

“…Recent studies performed by Sabo, Freeman, and Doll [29] have demonstrated that low-temperature thermodynamic properties of the cluster may be sensitive not only to the exact value of the confining radius, but also to the shape of the potential. Because the polynomial potential is not sufficiently flat for small values of r i − R cm when compared to a hardwall potential, a radius of at least R c = 2.65 σ LJ must be utilized in order to prevent the disappearance of the pre-melting solid-solid phase change [29]. However, beyond this radius, the vapor pressure depends only slightly on the exact value of the confining radius, for a large range of such values.…”

“…Clearly, such a state would have been made inaccessible by the small confining radius utilized by Neirotti et al In the present work, we utilize a confining potential in the form of a steep polynomial, which is more suitable for quantum simulations. It has been argued that, for such an analytical form of the confining potential, a larger confining radius of at least R c = 2.65 σ LJ is necessary in order to ensure that the low-temperature thermodynamic properties of the classical cluster are not significantly altered [29]. For quantum systems, one needs to worry about the possibility that the effects of quantum delocalization may lead to an even stronger influence of the confining radius on the structural properties of the Ne 38 cluster.…”

Structural Transitions and Melting in LJ74-78 Lennard-Jones Clusters from Adaptive Exchange Monte Carlo Simulations

“…10,11,[17][18][19] Depending on the structure of the global minimum, a LJ cluster may undergo one or more structural transformations according to the following general rules. Below size 31, the ground-state geometry is based on the polyicosahedral or antiMackay motif.…”

Study of Solid–Liquid Phase Changes of Lennard-Jones Nanoclusters by NPT Monte Carlo Simulations

“…The investigation of properties of small clusters is a subject of great theoretical and experimental interest. [1][2][3][4][5][6][7][8][9][10][11][12] The recent developments in nanotechnology gave new incentive to the study of clusters with diameters in the nanometer range (nanoclusters). The properties of such nanoclusters are very different than the properties of the bulk because of the large surface/volume ratio in the clusters.…”