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Phase Behavior of a Two-Dimensional Chiral Lattice Model

Thomas G. Lombardo1, Frank H. Stillinger2, and Pablo G. Debenedetti1. (1) Chemical Engineering, Princeton University, Princeton, NJ 08544, (2) Chemistry, Princeton University, Princeton, NJ 08544

The question of how the high enantiomeric excess of biomolecules emerged from a racemic environment has interested scientists for more than a century. Recent experiments on the phase behavior of the D and L forms of the amino acid proline suggest that asymmetric amplification can result from an initially small enantiomeric excess and certain aspects of equilibrium solid-liquid phase behavior [1]. We explore the phase behavior of a two-dimensional chiral lattice model via mean field theory. The interactions of the lattice model are chosen such that the phase behavior of the model qualitatively reproduces that of proline. Enantiopure and racemic crystals form above the solubility limit, and the racemic compound is energetically favored over the single enantiomer crystals. Our approach allows microscopic-level inquiry into the phase behavior of chiral systems, and into possible thermodynamic mechanisms for the emergence of chirality.


[1] Klussmann, M., Iwamura, H., Mathew, S. P., Wells, D. H., Pandya, U., Armstrong, A., and Blackmond, D. G., “Thermodynamic control of asymmetric amplification in amino acid catalysis”, Nature, 441: 621-623 (2006).