Anti-solvent crystallization of a ternary Lennard–Jones mixture performed by molecular dynamics

Abstract

Anti-solvent crystallization from a ternary mixture was examined by an NpT ensemble molecular dynamics simulation. The co-solvent and anti-solvent effects were represented by the Lennard–Jones interaction energy parameter, εij. The homogeneous binary solution of the solute and solvent was achieved at a constant temperature and pressure. Anti-solvent crystallization was introduced by changing some co-solvent molecules to anti-solvent molecules, immediately. The configuration of solute molecules was investigated by using the radial distribution function, g(r), and the local composition, xL. The value of εij affected the configuration of the solute molecules significantly; the decrease in εij provided the localization and crystallization of the solute molecules. The composition of the anti-solvent molecules in the solution also affected the configuration of the solute molecules; the increase in the anti-solvent composition produced the crystal structure of the solute molecules more rapidly. These qualitative results corresponded well to anti-solvent crystallization. The radial distribution function represented the crystal structure for solute molecules, and the local composition of the solute was increased from the bulk composition as the effect of the anti-solvent increased. We proposed that the time variation of the local composition of the solute represents the temporal development of the crystal structure and the time to crystallization well.