Microcanonical Thermodynamics of First Order Phase Transitions studied   in the Potts Model
  Phase transitions of first and second order can easily be distinguished in small systems in the microcanonical ensemble. Configurations of phase coexistence, which are suppressed in the canonical formulation, carry important information about the main characteristics of first order phase transitions like the transition temperature, the latent heat, and the interphase surface tension. The characterisitc backbending of the micro- canonical caloric equation of state T(E) (not to be confused with the well known Van der Waals loops in ordinary thermodynamics) leading to a negative specific heat is intimatly linked to the interphase surface entropy. 
D.H.E.Gross, A.Ecker and X.Z.Zhang (Hahn-Meitner Institut Berlin,   Germany)