Identifying Slip Planes in Organic Polymorphs by Combined Energy Framework Calculations and Topology Analysis

The relationship between crystal structure and mechanical properties is commonly studied by identifying slip planes through inspecting crystal structures visually, with a focus on the hydrogen bonding interactions. While useful, the visualization method lacks quantitative insight, and the identification of slip planes is subjective. Sometimes, crystal plasticity predicted from structure visualization does not match experimental crystal plasticity and powder tabletability as observed in three polymorphic systems, 6-chloro-2,4-dinitroaniline, indomethacin, and febuxostat. Here, we explored the feasibility of more reliably identifying slip planes by the energy framework approach, combined with analysis of potential slip layer topology. In all three cases, this new approach identified slip planes that are consistent with the observed mechanical plasticity and compaction behavior. Thus, it is superior to the visualization method for crystal structure analysis aimed at identifying active slip planes in organic crystals.