Melting of Lennard-Jones clusters in confined geometries

Abstract

The melting of Lennard-Jones (argon) clusters of various size (N"500 to 10000 atoms), confined in a rigid matrix, is studied by molecular dynamics simulations. For spherical clusters we show the existence of a cluster size below which the dependence of the melting temperature cannot be described by the classical GibbsThompson equation. We also provide evidence of the formation of a quasi-liquid layer at the surface of mesoscopic clusters. A good agreement is found between the theoretical model due to Celestini et al. and the simulation results obtained in this work. The melting of an ellipsoidal cluster is also investigated. We observe, in agreement with recent experimental and theoretical work, that the thickness of the molten layer is larger in the region of higher local curvature.

Molecular simulation of adsorption and intrusion in nanopores

“…This result shows that the validity of the Kelvin equation breaks down for pores having a diameter smaller than D ∼ 18σ . This value is consistent with previous studies which have shown that the Kelvin equation becomes inaccurate for pore sizes below 16σ (Fisher and Israelachvili 1981;Walton and Quirke 1989;Celestini et al 1996;Celestini 1997). We note that the condensation pressures found in the GCMC simulations can be fitted using the modified Kelvin equation provided the use of a unreasonably large Tolman length 2δ ∼ 2 nm (∼6.5σ ).…”

Melting and thermodynamic properties of rare gas nanocrystals

“…One of the most pronounced manifestations of change of thermodynamic properties observed in nanosized crystalline systems is the effect of reduction of the melting temperature of free nanocrystals [1][2][3][4][5][6][7][8][9]. So the principal problem of statistical description of thermodynamics of nanocrystals is elucidation of the mechanism of size effect on statistical characteristics of atoms in such systems.…”

“…Later, it was also established that this phenomenon has universal nature. It is inherent in any crystalline matter: metallic and semiconductor nanocrystals [2][3][4][5], rare gas [6,7] and ionic solids. It should be noted that depression of the melting point is observed only in free nanocrystals.…”

Grain size-dependent diffusion activation energy in nanomaterials

“…1 gives an example to confirm the validity of Eq. (8) where the earliest [20] and the latest [2] experimental results with different experimental techniques and computer simulation results [21] of Au are shown. Eq.…”

“…(6) where the experimental results [2,20] are predicted with d ¼ 1 while the computer simulation results [21] are done with d ¼ 0: This is because only the computer simulation may guarantee a free surface of nanocrystals. For both experimental results, the particles are either coated with porous silica shells [2] or deposited on substrate having an island shape [21], which leads to a quasi-dimension of one [9].…”