Isotopic and spin selectivity of H_2 adsorbed in bundles of carbon nanotubes

Due to its large surface area and strongly attractive potential, a bundle of carbon nanotubes is an ideal substrate material for gas storage. In addition, adsorption in nanotubes can be exploited in order to separate the components of a mixture. In this paper, we investigate the preferential adsorption of D_2 versus H_2(isotope selectivity) and of ortho versus para(spin selectivity) molecules confined in the one-dimensional grooves and interstitial channels of carbon nanotube bundles. We perform selectivity calculations in the low coverage regime, neglecting interactions between adsorbate molecules. We find substantial spin selectivity for a range of temperatures up to 100 K, and even greater isotope selectivity for an extended range of temperatures,up to 300 K. This isotope selectivity is consistent with recent experimental data, which exhibit a large difference between the isosteric heats of D_2 and H_2 adsorbed in these bundles.Comment: Paper submitted to Phys.Rev. B; 17 pages, 2 tables, 6 figure

Not Available

Not AvailableDetailed soil survey was carried out in parts of Tan Command area which lies in the flood plain of Narmada and Tawa rivers. The soils belong to Vertisols and associated shrink-swell soils. Properties of two soil series, viz. Rohana-1 (Rhl) and Rohana-2 (Rh2) are described; the former being cultivated and the latter uncultivated. Clay content of the two soils is comparable, through RhI soils have higher clay content. Infiltration rate is lower in RM than in Rh2 soils. There is an increasing trend of Na, Mg/Ca ratio and ESP values with depth for Rhi, but usually insignificant for Rh2. Well water (W1) has higher values of pH, Na, Mg/Ca ratio, residual sodium carbonate (RSC) and SAR than canal irrigation water. It is thus envisaged that use of such ground water with lower EC and higher Na values (which is potentially sodic), may deteriorate the soil structure and decrease the infiltration rate by causing dispersion of clays. Moreover, systematic soil survey helped to identify and show that for shrink-swell deep black soils, irrigation even with slightly poor quality water may be hazardous for soil environment in the Tawa Command regionNot Availabl

Quantum effect induced kinetic molecular sieving of hydrogen and deuterium in microporous materials

We report here our investigations using Monte Carlo and molecular dynamics (MD) simulations, as well as quasi-elastic neutron scattering experiments, to study the adsorption and diffusion of H-2 and D-2 in zeolite Rho. In the simulations, quantum effects are incorporated via the Feynman-Hibbs variational approach. At low temperatures, we observe a reversal of kinetic molecular sieving in which D-2 diffuses faster than H-2. Based on fits of bulk data, we suggest new set of potential parameters for hydrogen, with the Feynman-Hibbs variational approach used for quantum corrections. The transport properties obtained from MD simulations are in excellent agreement with the experimental results, with both showing significant quantum effects on the transport at low temperature. The MD simulation results on two different structures of zeolite Rho clearly demonstrate that the quantum effect is very sensitive to pore size. High transport flux selectivity is noted at low temperatures, suggesting feasibility of kinetic isotope separation