Predicting the occurrence of reflection twins

This paper describes a method for predicting which surfaces of a crystal can form reflection twins. The algorithm has been successfully applied to six inorganic crystal systems ranging from simple salts (corundum and rutile) to more complicated systems containing molecular ions (aragonite, gibbsite, sodium oxalate and zircon). Our approach calculates the difference between the attachment energies of twinned and untwinned growth slices. The occurrence of planes that result in a small difference of energy (<1% of the intermolecular lattice energy) correlates with all the commonly observed twinning in these systems.