(227h) Phase Diagrams By Computer Simulations: A Good School for Force Fields

After the initial steps of computer simulations when simulations
were performed mostly for just a certain thermodynamic state, the determination
of phase equilibria from computer simulations has been an area of
growing interest. Although the fluid-solid equilibria of hard spheres was the
first example, most of the work was devoted to the determination of
vapor-liquid equilibria and often force fields parameters were
determined by fitting vapor-liquid equilibria. However the idea
that fluid-solid equilibria could be useful to learn the basic
physics about molecular systems was gaining interest after the work
of Peter Monson and coworkers using simple potential models.
The work with him moved me to consider the possibility that
fluid-solid equilibria could also be used to determine the parameters of the intermolecular potential.
In the last three decades it has been shown that
fluid-solid equilibria can be determined by computer simulations using
several methods (direct-coexistence, free energy calculations ).
That allowed to propose reasonable potential models for molecules as
important as water. In the last years it has been realized that the determination of the
solubility of a solid in a solvent by computer simulation is feasible and
we will shown how this can also be used to propose improved pair potentials
for salts in water. Obviously the determination of the equilibrium
conditions is the first step for addressing nucleation studies.
Thus, this is a short summary of a trip that I started in Amherst with Peter , twenty five years
ago.