EQUATION OF STATE FOR HYDROGEN-BONDED SYSTEMS

Hydrogen-bonded systems have a surprisingly simple equation of state i n the mean field approximation. If we know the equation of state P-ref (T, V, N-1, N-2, ...) of the reference system (without hydrogen bonds) , then the equation of state of the system with hydrogen bonds can be written as P(T, V, N-1, N-2, ...) = P-ref(T, V - Sigma (VijMij)-M-H, N -1, N-2, ...) - kT Sigma M-ij/V, where M-ij is the number of bonds of the corresponding kind and V-ij(H) is the volume change upon a bond fo rmation. It is interesting that this equation is valid for fluids, gas es, solids-as long as the system is far from the critical point and th e basic presumptions of the mean field theory are valid. This equation as well as other useful thermodynamic relations for hydrogen-bonded s ystems are proved, and their consequences are discussed.