A QUANTITATIVE-ANALYSIS OF THE RELATIVE IMPORTANCE OF SYMMETRY OPERATORS IN ORGANIC MOLECULAR-CRYSTALS

The contribution of each symmetry operator to the lattice energy is calculated for a sample of 1068 non-hydrogen-bonded crystal structures in the most frequent space groups for organic molecules. The molecular coordination sphere is defined as the ensemble of neighbouring molecules each of which contributes more than 2% of the packing energy, and some geometrical aspects of this ensemble are studied. The frequency with which each operator is the most relevant one is estimated for each space group. It appears that some operators dominate, while others are silent by-products of the combinations of dominant ones. Pure translation gives the top contribution to the packing energy in a significant number of cases.