On the structure of liquid helium

An analytical expression for S(k), the structure factor, has been derived treating the square-well potential as a perturbation as a perturbation on the hard-core in the mean spherical model approximation. A fit has been made to the first peak maximum at T=4.2 K which is above the Λ-transition (T=2.19 K) temperature so as to get not only a satisfactory peak height at the fitted temperature but also over a range of temperatures (both above and below the Λ-transition) and densities. At high temperatures, the computed values agree fairly well with experiment while the discrepancy between the calculated and experimental values is pronounced at low temperatures. This might be due to the fact that quantum effects are pronounced below the point. (author)