A new polymorph (IV) of benzamide: Structural characterization and mechanism of the I ⇆ IV phase transition

We present a molecular simulation study dedicated to the manifold of benzamide crystal structures. Along this line, a new polymorph (IV) is identified and structurally characterized. The new polymorph exhibits the same hydrogen bonded network as the stable form (I), but differs in the arrangement of molecular layers. From high-pressure molecular dynamics simulations, the I-IV transformation mechanism is suggested as the anti-parallel shuffling of (010) layers along the [100] direction. This results in a more compact benzole ring stacking and an increase in density. Thus, high-pressure synthesis is suggested as a route to the yet unconfirmed polymorph IV. (C) 2011 Elsevier B. V. All rights reserved.