${}^4\mathrm{He}$ adsorbed inside (10,10) single-walled carbon nanotubes

Diffusion Monte Carlo calculations on the adsorption of ${}^4\mathrm{He}$ in open-ended single-walled (10,10) nanotubes are presented. We have found a first order phase transition separating a low-density liquid phase in which all ${}^4\mathrm{He}$ atoms are adsorbed close to the tube wall and a high-density arrangement characterized by two helium concentric layers. The energy correction due to the presence of neighboring tubes in a bundle has also been calculated, finding it negligible in the density range considered.

Figure 1

Energy versus density for different elections of the trial function: One-layer liquid (full circles, squares, two-layer liquid circles), and close to the wall solid (full squares).

Figure 2

Maxwell construction to determine the stability range of the phases involved in the modeling of the system. Full line, one-layer liquid and $\text{solid}+\text{liquid}$ phases; circles, two-layer liquid phase.

Figure 3

Radial density profiles at zero pressure (dashed line) at the lower and upper limits of the coexistence regions (dotted and long-dashed lines, respectively). The solid line represents the case for the $\text{solid}+\text{liquid}$ phase at the highest density simulated.