Virtual Tensile Test for Brittle, Plastic, and Elastic Polymorphs of 4-Bromophenyl 4-Bromobenzoate

We report on the development of a novel methodology for computational predictions of the mechanical properties for single crystals. This methodology is based on constrained optimization using dispersion-corrected density functional theory level, and can be dubbed the virtual tensile test. The approach was validated on the example of 4-bromophenyl 4-bromobenzoate, an organic compound known to form three polymorphs with different mechanical characteristics. Each one of these polymorphic crystal structures was stretched stepwise along each crystallographic axis, while the remaining lattice parameters and atomic coordinates were relaxed. The geometrical properties of halogen bonds and the other noncovalent interactions were monitored at each step to understand the nature of mechanical response. The unit cell volumes and lattice energies were plotted as functions of the stretching parameter, and these curves were analyzed in terms of mechanical properties of the brittle, plastic, and elastic polymorphs.