Simplified gauge-cell method and its application to the study of capillary phase transition of propane in carbon nanotubes

Abstract

A modification of the gauge-cell method for Monte Carlo studies of phase equilibrium in nano-confined systems is presented and employed for studying the capillary phase transition of propane in single-walled carbon nanotubes as a function of tube diameter. It is shown that if an analytical equation of state for the vapor phase is known, the acceptance rule for the trial move of particle exchange can be modified to reference the bulk system through its chemical potential. Under these conditions, the simulation procedure is simplified and acquires many characteristics of a Monte Carlo simulation conducted in the grand canonical ensemble. It is also shown that the critical temperature can be estimated by interpolation of sub-and supercritical values of the slope of the inverse isotherm at the inflection point. To enhance the sampling of propane molecules in the hollow space of the nanotubes the configurational-bias scheme is employed. The simulation results show that the confinement of propane increases its critical density, reduces the critical temperature and narrows the binodal curve with decreasing tube diameter until the system approaches one-dimensional behavior.

Pharmacological and toxicological target organelles and safe use of single-walled carbon nanotubes as drug carriers in treating Alzheimer disease

“…Therefore, currently brain ACh can only be increased by clinical administration of certain mild inhibitors of acetylcholinesterases that hydrolyze ACh. 53 Because SWCNTs have the ability to absorb inorganic 54,55 and organic chemicals, [56][57][58][59][60] in addition to the ability to enter the brain via nerve axons, so they are ideal for the delivery of ACh molecules. At the same time, ACh is composed of an acetyl group and a quaternary ammonium group, which allows for its easy absorption by SWCNTs.…”

Determination of phase equilibria in confined systems by open pore cell Monte Carlo method

“…Because of the excellent suitability of this method for the confined inhomogeneous system, the gauge cell method has been used for studies of vapor-liquid coexistences in various systems. [33][34][35][36][37][38][39][40][41][42][43][44] However, according to Vishnyakov and Neimark, 33 the method is not suited for a system at low temperatures such that the confined fluid enters into a glass or crystalline state, because very few attempts of particle exchange are successful, making it difficult to reach equilibrium. Moreover, significant computational effort is required for optimizing the size of the gas cell and to obtain a continuous sigmoid adsorption isotherm required for precise thermodynamic integration.…”

Calculation of chemical potentials of chain molecules by the incremental gauge cell method

“…31 MCMC has been extended from its original formulation 22 to extremely small confinements with the ideal gas gauge cell (IGGC) method, 23 mixtures with multi-component gauge cell method, 24 coupling with Widom insertions, 32 configurational bias, 33 and simplified insertions using explicit chemical potential. 34 To extend MCMC to linear homopolymers, we begin by considering a system cell that contains a polymeric fluid of one or more chains of identical monomers, and a gauge cell that contains a fluid of ideal non-bonded monomers. Standard MC moves are used to sample state space in the system cell; this work includes monomer displacement and reptation of the chain (but can also include configurationally biased regrowth or any other canonical ensemble move to equilibrate the chain in the system cell), particle insertion from the gauge into the sample cell, and particle removal from the sample cell to the gauge cell.…”