Monte Carlo and molecular dynamics simulation of argon clusters andn-alkanes in the confined regions of zeolites

Abstract

Geometry and energy of argon clusters confined in zeolite NaCaA are compared with those of free clusters. Results indicate the possible existence of magic numbers among the confined clusters. Spectra obtained from instantaneous normal mode analysis of free and confined clusters give a larger percentage of imaginary frequencies for the latter indicating that the confined cluster atoms populate the saddle points of the potential energy surface significantly. The variation of the percentage of imaginary frequencies with temperature during melting is akin to the variation of other properties. It is shown that confined clusters might exhibit inverse surface melting, unlike medium-to-large-sized free clusters that exhibit surface melting. Configurational-bias Monte Carlo (CBMC) simulations of n-alkanes in zeolites Y and A are reported. CBMC method gives reliable estimates of the properties relating to the conformation of molecules. Changes in the conformational properties of n-butane and other longer n-alkanes such as n-hexane and n-heptane when they are confined in different zeolites are presented. The changes in the conformational properties of n-butane and n-hexane with temperature and concentration is discussed. In general, in zeolite Y as well as A, there is significant enhancement of the gauche population as compared to the pure unconfined fluid.

Understanding the Role of Sodium during Adsorption: A Force Field for Alkanes in Sodium-Exchanged Faujasites

“…33 They used the same set of parameters as Mellot et al 12 in their simulations of chloroform in NaY. Finally, Yashonath et al have also performed simulations of propane, 37,38 n-butane, 39 and several n-alkanes 40 in NaY but again discounting sodium mobility.…”

Adsorption of Guest Molecules in Zeolitic Materials: Computational Aspects

“…This topic, which dates back to the late 1970s, has been partly reviewed before, − and we shall concentrate here on the substantial amount of work that has appeared in this area in the past decade (Tables and , − <...…”

Solvation shell structure of cyclooctylpyranone in water solvent and its comparative structure, dynamics and dipole moment in HIV protease

“…On many occasions in chemistry and biology one comes across confinement effects, and the effect has been studied in systems such as organic molecules, inorganic ions 15 and atomic 16 and molecular clusters. 17 Usually the confinement discussed is the spatial confinement created within supramolecules, mesoporous materials (such as zeolites) or cavities formed by the solvents.…”