SQUARE-WELL FLUID AT LOW DENSITIES

Values for the radial distribution function and the direct correlation function at low densities and for the first five virial coefficients are obtained for a fluid of molecules interacting according to the square-well potential when the width of the attractive well is half the radius of the hard core. It is found that the higher-order coefficients are surprisingly large and, as a result, the virial series fails to converge even at temperatures and volumes significantly greater than the critical temperature and volume. Comparisons of these exact virial coefficients with those given by several approximate theories are made. Values are also given for the first five virial coefficients when the width of the attractive well is equal to the radius of the hard core.