A fully automatic program for finding the unit cell from powder data

A description is given of a fully automatic program, written in ALGOL 60, that finds the constants of the reciprocal lattice from powder data. The progress of the program is illustrated with the (nearly) complete computer output for one selected case. Planes through the origin of the reciprocal lattice (zones) are found first. After evaluating these, the program selects pairs of zones with a common row in order to find reciprocal lattices, which are then reduced in a simple way. Each solution is compared with the experimental data and a figure of merit is calculated. The program is most suited for compounds of orthorhombic or lower symmetry.