Theoretical Study of the Crystal Growth Mechanism of the Energetic Metal–Organic Framework [Na3(DNT)(H2O)]n Based on Metadynamics

Energetic metal–organic frameworks (EMOFs) are promising high-energy, low-sensitivity materials; however, their atomic-scale crystal growth mechanisms remain poorly understood. Here, we combined ab initio molecular dynamics simulations with metadynamics to investigate the early-stage crystal growth on the (001), (010), and (100) facets of a Na + -coordinated 1,2,4-dinitroaminotriazole (DNT)-based EMOF in an explicit aqueous solution. Free DNT ligands can be stacked layer by layer in an ordered manner, following the ideal lattice arrangement, only when Na + ions are distributed at appropriate positions on the crystal facets and multiple coordination bonds formed simultaneously on both sides of the ligand. In contrast, single Na + bridging or coordination on the same side of the ligand leads to disordered packing. The coordination structure formed on the (001) facet exhibits the highest stability among the three facets, making it the most favorable growth facet. More importantly, the (001) facet has the lowest Na + diffusion barrier along its intermolecular channels, which is lower than those of the other facets and kinetically explains its preferential growth.