Crystal growth mechanism determined by crystallographic and affine symmetries. Part II

As shown in Part I, in the case of organic substances with two crystallogra phically independent molecules, crystallographic and affine symmetries dete rmine crystal growth. The Fourier transform method was used to calculate th e theoretical growth forms. The morphological lattice necessary for these c alculations can be derived from an affine or klassengleiche supergroup of t he structural space group. It can be shown that growth is influenced not on ly by the geometric effectiveness: of the symmetry elements: but also by ph ysical factors such as differences in conformation and external factors. Th e theoretical growth forms were also calculated using attachment energies ( Hartman method). A better correspondence to the observed crystals is obtain ed when the affine symmetries are also considered in these calculations. Fo r these investigations, the crystal structures of 2,3-dichloro-1,4-naphthoq uinone, amidopyrine (P (1) over bar), glycolic acid, malonamide and cyanoac etamide (P2(1)/c) were used. All of these structures contain two crystallog raphically independent molecules in the unit cell.