Second virial coefficients of two-dimensional helium: The Beck potential

The second virial coefficients of two-dimensional systems of ${\mathrm{He}}^3$ and ${\mathrm{He}}^4$ have been calculated assuming that the atoms interact via the Beck potential. The virial coefficient and its contribution to the specific heat are almost the same as calculated previously with a Lennard-Jones potential. Therefore small discrepancies between experimental data and our previous calculation are ascribed to effects of the substrate.