Molecular modeling of cryogenic hydrogen behavior in vapor–liquid equilibria and confinement

Abstract

We report the effect of Feynman–Hibbs corrections on the intermolecular potential to take into account the quantum effects of hydrogen at low temperature and high density for vapor–liquid equilibria (VLE) and confinement into carbon nanotubes. Density against temperature, pressure against temperature and isochoric curves are displayed for VLE, while adsorption isotherms for different pore sizes and different temperatures are showcased to see the effect under confinement. Besides, 5 different models for hydrogen are employed; one atomistic and 4 coarse-grained models, covering both classical and quantum approximations. For the case of VLE we observed that the quantum corrected models lead to more accurate and reliable results in good agreement with the experimental data. The adsorption isotherms produced with the different models showed that the difference between quantum and classical approximations are significant for maximum confinement (smallest pore) and lowest temperature (77K). As we increase both the temperature and the pore size, the difference between the different models become less noticeable.