Atomic-potential parameters for H2 and D2: quantum corrections in the calculation of second-virial coefficients

First-order quantum corrections were introduced into the computation of the second-virial coefficients of H₂ and D₂. The quantum effects, for the studied two light molecules, are considerable even at the room temperature and become prominent at low temperatures. Atomic potentials, incorporating the quadrupole interactions, were employed in the calculations. Optimum atomic-potential parameters ε_H, σ_H, ε_D and σ_D were obtained from the nonlinear least-squares fit of the experimental second-virial coefficients. The fitted virial coefficients cover the temperature ranges of 173-423 and 153- for H₂ and D₂, respectively.