Polymorphism, twinning and morphology of crystals of 2,4,6-trinitrotoluene grown from solution

Crystals of 2,4,6-trinitrotoluene (TNT) have been grown from a wide range of organic solvents under various conditions. The structural nature and morphology of these crystals were systematically characterised using a number of techniques. The crystals were found to exist in two basic forms having monoclinic and orthorhombic structures. The monoclinic modification was the stable form from ambient temperature to the melting point and showed extensive twinning: the twin law was defined and the structural origin of twinning determined. The variation in crystal morphology with growth conditions for the monoclinic modification was attributed to the small differences in reticular areas for morphological forms other than {100}. The structural perfection of monoclinic crystals was shown to be dominated by impurity-related defects.