Modelling fluids and crystals using a two-component modified phase field   crystal model
  A modified phase field crystal model in which the free energy may be minimised by an order parameter profile having isolated bumps is investigated. The phase diagram is calculated in one and two dimensions and we locate the regions where modulated and uniform phases are formed and also regions where localised states are formed. We investigate the effectiveness of the phase field crystal model for describing fluids and crystals with defects. We further consider a two component model and elucidate how the structure transforms from hexagonal crystalline ordering to square ordering as the concentration changes. Our conclusion contains a discussion of possible interpretations of the order parameter field. 
Mark J. Robbins, Andrew J. Archer, Uwe Thiele and Edgar Knobloch
cond-mat.soft