Enhancement of the `auto-indexing' method for cell determination in four-circle diffractometry

Enhancements in the auto-indexing procedure for cell determination improve its power and reliability. A proper selection of three basis reflections for construction of an initial subcell is essential. A standard cell-reduction procedure applied to the subcell, and the calculation of appropriate limits for the direct-lattice-vector generation integers, make a comprehensive coverage of the direct space efficient and effective. Refinement of the generated lattice vectors against all the available reflection data makes assignment of the correct unit cell easier and more reliable. Generation of some additional long vectors is recommended in special cases.