Renormalization-group corrections to an approximate free-energy model for simple fluids near to and far from the critical region

We combine liquid-state theory with a renormalization-group method to develop an equation of state for simple fluids that is valid near and far from the critical point. The resulting equation of state has nonclassical critical exponents close to those experimentally observed. Far away from the critical point, the equation of state reduces to that obtained by liquid-state theory. This formalism is applied successfully to square-well fluids, and to three real fluids: methane, carbon dioxide, and n-butane. © 1998 American Institute of Physics.