Simulating vapour growth morphology of crystalline urea using modified attachment energy model

We report a computational model to simulate vapour growth morphology of urea crystal by considering molecular anisotropy and surface relaxation of different crystal faces. It has been argued that the faces' growth occurs through the adsorption of molecular layers rather than a slice of thickness dhkl. The molecular layer is a 2-D periodic arrangement of molecules in which each molecule has same the orientation. The molecular orientations in a slice of thickness dhkl may differ from each other and depend on crystallographic orientation of the slice. The discussed approach has been employed to simulate vapour growth shape of crystalline urea by calculating attachment energy of molecular layers using Hartee–Fock and density functional theories. The calculated growth morphology is in good agreement with the vapour grown shape of urea crystal. The role of thermal and growth kinetics affecting the vapour growth morphology has been discussed. The observed polar growth morphology of urea crystal has also been discussed particularly in the context of different atomic environments of (111) and (−1−1−1) faces.

► Modified attachment energy model is used to simulate vapour shape of urea crystal. ► Molecular anisotropy and surface relaxation on growth morphology were investigated. ► An ab initio method is employed to obtain energetics of molecular layers. ► The effect of thermodynamic and growth kinetic on growth morphology is discussed. ► Polar shape of urea crystal is discussed using different surface structures.