Light isotope separation in carbon nanotubes through quantum molecular sieving

The theoretical basis for the phenomenon of quantum sieving is detailed for confined one-dimensional systems. A simple theory is presented to calculate zero-pressure selectivities due to quantum sieving in nanopores. This simple theory is used to evaluate the ability of various carbon nanotubes and interstices of nanotubes to separate mixtures of light-isotope species. Realistic and accurate potentials are used for the interactions between adsorbates and nanotubes. Path integral molecular simulations are also used to determine quantum sieving zero-pressure selectivities. Good agreement is found between the simple theory and detailed path integral calculations. Systems of ${\mathrm{H}}_2-{\mathrm{T}}_2,$ and ${}^3\mathrm{He}{-}^4\mathrm{He}$ are studied in this work, as well as ${\mathrm{CH}}_4-{\mathrm{CD}}_4$ and ${\mathrm{H}}_2-\mathrm{HD}.$