Equilibrium Thermodynamics of the Dimers and Trimers of H(2) and D(2) and Their Heterodimer (H(2))(D(2))

[Image: see text] The equilibrium thermochemical properties of the dimers and trimers of H(2) and D(2) are obtained from the equations of state (EOSs) of normal H(2) and D(2). The standard dimer and trimer equilibrium constants K(D)(o) and K(T)(o) and ΔH(D, T)(o) and ΔS(D, T)(o) are reported for these weakly bound van der Waals molecules between 25 and 45 K. Statistical thermodynamics (ST) calculations of H(2) and D(2) dimerization using Morse pair potentials to account for intermolecular interactions, obtained from recent experimental work, are in qualitative agreement with the EOS results. The entropies of the H(2) and D(2) dimers and trimers are calculated from the EOS ΔS(o) values and ST calculations of the monomer entropies.