Understanding the growth morphology of explosive crystals in solution: insights from solvent behavior at the crystal surface
The structural, energetic, and dynamic properties at the interfaces between the five growth faces of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) crystal and acetone (AC) solvent were investigated by computational simulations with an aim to understand the RDX crystal morphology when grown from AC solvent at the molecular level. The simulation results showed that the solvent behavior, such as the mass density distribution, dipole orientation, interaction, and diffusion, was dependent on the structural features of each crystal surface. The binding sites for solvent incorporation at the crystal surface were found and were visually displayed on the basis of occupancy analysis. The typical binding motifs were extracted from the simulation trajectory, with the corresponding binding affinities estimated as (002) ≈ (210) > (200) > (020) > (111) at the M06-2X/6-31++G** level of theory. The theoretical prediction of the morphological importance of each growth face was in reasonable agreement with the experimental RDX morphology grown from AC solvent.