Optmizied random phase approximation for the phase diagram of C60 material

This paper determines the phase diagram of C60 fluid by an efficient and robust optimized random phase approximation (ORPA) method of Pastore et. al (1995), imposes physical requirements as in the original ORPA scheme with a view to achieving consistency within the liquid structure factor. Our perturbation/variational approach for the Helmholtz free energy of the C60 molecules is based on the Lennard-Jones intermolecular interaction. We observe that higher accuracy is obtainable by treating all the grid points within the exclusion hole of the pair distribution function as independent variables. Our numerical results show appreciable improvement in both the thermodynamic functions and the structure factor. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 21-2