Isotopic difference in the second virial coefficient of water: another test of the MCY-B description of water dimer thermodynamics

The component of the second virial coefficient of steam related to the formation of dimers is evaluated. The necessary equilibrium constants of dimerization were evaluated within the MCY-B water pair interaction potential. The calculated isotopic difference in the second virial coefficient reflects the qualitative features found by observation but, nevertheless, the calculation quite distinctly overestimates the value of this isotopic difference as compared with the observation. The nature of these differences and the relation to the state behaviour of water are discussed. (author) 34 refs.; 1 tab