  An atomic-scale model for silicate solutions is introduced for investigation
of the nucleation process during zeolite synthesis in the absence of a
structure directing agent. Monte Carlo schemes are developed to determine the
equilibrium distribution of silicate cluster sizes within the context of this
model. How the nucleation barrier and critical cluster size change with Si
monomer concentration is discussed. Distance and angle histograms as well as
ring size distributions are calculated and compared with known zeolite
structures. The free energies of critical clusters are compared with those for
small clusters of alpha-quartz.
