A Mean Field Theory approach to a model with Dipole-Quadrupole   interaction
  We study a model initially proposed to describe a mixture of (CO) and (N2) adsorbed on exfoliated graphite. The approach used here is that of mean field theory. The Mean Field equations and the Helmholtz Free Energy are found. Phase diagrams are calculated too, and it is possible to find an analytical expression for the second order phase transition line. 
R.P.B. Santos