THE EQUATION OF STATE FOR MOLECULES WITH SHIFTED LENNARD-JONES PAIR POTENTIALS

Compressibility factors and internal energies have been calculated for fluids with softly repulsive pair potentials by means of the Maxwell distribution method. The pair potentials used are Lennard-Jones potentials, truncated at the minimum and with the minimum shifted towards zero energy. The exponent of attraction has been varied between 4 and 8, the exponent of repulsion between 8 and 40. An empirical equation of state has been developed which permits the calculation of thermodynamic properties for all truncated Lennard-Jones potentials. When this equation of state is substituted for the hard-sphere term in simple equations of state of the var der Waals type, a better representation of caloric data is obtained, especially over the high density region.