GROWTH OF M-CHLORONITROBENZENE CRYSTALS IN THE PRESENCE OF TAILOR-MADE ADDITIVES - ASSIGNMENT OF THE POLAR AXES FROM MORPHOLOGICAL CALCULATIONS

The influence of the structurally similar additives, o-chloronitrobenzene (o-CNB), p-chloronitrobenzene (p-CNB), p-dichlorobenzene (p-DCB), and p-dinitrobenzene (p-DNB), on the morphology of m-chloronitrobenzene (m-CNB) crystals has been investigated theoretically and experimentally. Both experiments and predictions confirmed the strong polar morphology of m-CNB crystals grown in the presence of the additives p-CNB and p-DNB. Calculations indicate strong binding interactions of these molecules with crystal surfaces at one end of the polar [001] growth direction. Experiments confirm this through the observed rounding and development of polar morphology along the c-axis. The predicted forms were found to be in good agreement with the observed morphologies. The influence of o-CNB in modifying the morphology of m-CNB crystals was found to be less significant than predicted while p-DCB had no effect. These results suggest that the presence and position of the nitro functional group in the tailored additive molecules directs the preferential adsorption of the molecules to one end of the [001] direction of the m-CNB crystals. The effects of the additives on the crystal morphology of m-CNB can therefore be explained by a mechanism in which particular functional groups on the additive molecule influence crystal growth in specific crystallographic directions.