processPIXEL: a program to generate energy-vector models from Gavezzotti's PIXEL calculations

A command-line program is presented to convert the output from Gavezzotti's PIXEL calculations to Shishkin's energy-vector models representing the intermolecular interaction topology. The output models comprise sets of vectors joining the centres of the molecules in a crystal structure, scaled so that the vector representing the most stabilizing pairwise interaction has length equal to half of the corresponding intermolecular separation. When the energy-vector model is packed, the most stabilizing pairwise interaction is represented as a continuous line between interacting molecules, while the other intermolecular interactions are shown as discontinuous lines, with a smaller gap representing a more stabilizing interaction. The energy-vector models can be overlaid on the crystal structure using the Mercury visualizer to enable convenient visualization of structural motifs that contribute significantly to the overall crystal packing energy.