Structure and Dynamics of Benzene in One-Dimensional Channels

Abstract

Molecular dynamics investigation of benzene in one-dimensional channel systems AlPO4-5, VPI-5, and carbon nanotube is reported. The results suggest that, in all the three host systems, the plane of benzene is almost perpendicular to the channel axis when the molecule is near the center of the channel and the plane of benzene is parallel to the channel axis when the molecule is near the wall of the channel. The density distribution of benzene as a function of channel length, z, and the radial distance, r, from the channel axis is also different in the three host structures. Anisotropy in translational diffusion coefficient, calculated in body-fixed frame of benzene, suggests that benzene prefers to move with its plane parallel to the direction of motion in AlPO4-5 and VPI-5 whereas in carbon nanotube the motion occurs predominantly with the plane of the benzene perpendicular to the direction of motion. Anisotropy associated with the rotational motion is seen to alter significantly in confinement as compared to liquid benzene. In AlPO4-5, the rotational anisotropy is reversed as compared to liquid benzene thereby suggesting that anisotropy arising out of molecular geometry can be reduced. Reorientational correlation times for C 6 and C 2 axes of benzene are reported. Apart from the inertial decay of reorientational correlation function due to free rotation, two other distinct regimes of decay are observed in narrower channels (AlPO4-5 and carbon nanotube): (i) an initial fast decay (0.5−2 ps) and (ii) a slower decay (>2 ps) of reorientational correlation function where C 6 decays slower than C 2 similar to what is observed in liquid benzene. In the initial fast decay, it is seen that the decay for C 6 is faster than C 2 which is in contrast to what is observed in liquid benzene or for benzene confined in VPI-5.

Diffusion in tight confinement: A lattice-gas cellular automaton approach. I. Structural equilibrium properties

“…We use our LGCA to examine the influence of site energy heterogeneity by investigating competitive adsorption of guest molecules at different sites. Following the lines of Bhide et al 20 we choose the energy parameters as ex = 10 kJ/ mol and in = 20 kJ/ mol. The choice to differentiate two types of site into each cell arises from the experimental evidence of two different types of adsorption locations in various zeolites, 11 or more generally, of n types of sites differing in their ability to bind a guest species.…”

“…We differentiate the statistical weight of the two kinds of site by assigning them a different energy ͑lattice gases with two nonequivalent sites were extensively studied by Chvoj et al, 15 Tarasenko et al, 16 and by Bhide et al 20 through KMC simulations͒. We denote − ex the energy of an exit site and − in the energy of an inner site.…”

A novel algorithm to model the influence of host lattice flexibility in molecular dynamics simulations: Loading dependence of self-diffusion in carbon nanotubes

“…Bhide and Yashonath investigated the dynamics of different molecules in CNTs. [33][34][35][36] In all cases they observed superdiffusive motion. This can be attributed to the way in which they analyzed the mean-squared displacement ͑see Sec.…”

“…Most probably this applies also to their other studies. 33,35,36 It is well known that at short times the MSD always displays a ballistic regime. 60 Furthermore, the time it takes to go over to the normal-mode diffusion is, for particles confined in CNTs, much higher than for particles confined in zeolites ͑due to the smoothness of CNTs͒.…”

The influence of geometric heterogeneity of closed carbon nanotube bundles on benzene adsorption from the gaseous phase-Monte Carlo simulations

“…Membranes composed of carbon nanotubes (so-called carbon nanotube forests) have been recently synthesized and found to function well as environmental sensors or superior adsorbents for removing many kinds of organic pollutants such as dioxin and volatile aromatic organic compounds from air streams and aqueous solutions, and of course C 6 H 6 (Agnihotri et al 2005;Bittner et al 2003;Castillejos et al 2012;Eswaramoorthy et al 1999;Jing et al 2004;Long and Yang 2001;Peng et al2003;Penza et al2004;Podkościelny et al 2014;Star et al2003;Sumanasekera et al 2002;Wiśniewski et al 2015a). The problem of adsorption of organic compounds inside carbon nanotube (CNT) type materials has been also discussed on the basis of theoretical studies (Bhide and Yashonath 2000;Irving et al 2004;Menon et al 2000;Pańczyk et al 2014;Podkościelny et al 2014;Takaba et al 1995;.…”