The effects of P-T changes on intermolecular interactions in crystal structure of iodoform

The structural transition at different pressures of a halogen and
hydrogen bonded molecular structure (iodoform, CHI3) is described. The
pressures analyzed up to sample decomposition are 0.85 GPa (P1RT) and
2.15 GPa (P2RT); also room conditions (PORT) and low temperature (106 K,
POLT) structures have been reported for comparison. The observed
disorder-order phase transition, from P6(3)/m to P6(3) space group, can
be rationalized by the intermolecular interaction analysis. The
shortening of the distances among iodoform planes, observed during the
compression and the temperature decreasing, determines an ordering of
molecular dipoles in a parallel arrangement: this phase transition
causes a shortening of I center dot center dot center dot I halogen
bondings. The BSSE corrected cohesive energies have been calculated for
all structures at DFT/B3LYP level of theory using a periodic boundary
condition code and the Grimme dispersion correction. Hirshfeld surfaces
and electrostatic potential mapped on charge density isosurfaces have
been computed and their features have been analyzed, in order to better
understand the halogen intermolecular interactions that control the
structural modification of iodoform crystal. (C) 2013 Elsevier B.V. All
rights reserved.