The effects of aluminum-silicon ordering on phase separation for a two-dimensional model of alkali feldspars

The time evolution of a model system for mixtures of sodium and potassium feldspars is investigated by computer simulations in order to determine what effects aluminum-silicon ordering may have on phase separation in these minerals. We assume that there is a greater energetic advantage for Al atoms to move onto preferred sites in the vicinity of Na atoms than in the vicinity of K atoms. This couples Al/Si ordering to the phase separation. We find that in such a system phase separation is slowed substantially compared to a system in which the two processes are not coupled.