Possible "new" quantum systems. II. Properties of the isotopes of spin-aligned hydrogen

The ground-state and finite-temperature properties of spin-aligned hydrogen and its isotopes (H↑, D↑, T↑) are studied theoretically. Calculations of the ground-state energy are presented for the Kolos-Wolniewicz (KW) potential and compared to those utilizing Lennard-Jones (LJ) and Morse potentials fit to the KW potential. Excellent agreement between the KW and LJ results is found; thus, permitting confirmation of previous predictions that H↑ can never form a liquid phase. In addition, spin-aligned deuterium with one (${\mathrm{D}\mathrm{\uparrow }}_1$) and two (${\mathrm{D}\mathrm{\uparrow }}_2$) allowed nuclear spin states is also studied. Ground-state energies and relevant zero-temperature critical parameters are presented for these systems. Additionally, the quantum theorem of corresponding states is used along with the ground-state results to estimate the critical parameters of ${\mathrm{D}\mathrm{\uparrow }}_1$ and ${\mathrm{D}\mathrm{\uparrow }}_2$. Finally, the effect of quantum mechanics on the critical behavior of these systems is considered and it is concluded that such effects are not likely to be observable.