Compound identification and characterization using lattice-formula matching techniques

A lattice-formula matching technique has been developed to be used in conjunction with the NBS Crystal Data File [(1982), National Bureau of Standards, Gaithersburg, MD] for the identification and characterization of crystalline materials. This technique is reliable, efficient and highly selective. In the first step of the identification/characterization procedure, a unit cell defining the lattice is determined. The cell is reduced and derivative supercells and subcells are calculated. These cells are then checked against the NBS Crystal Data File in which all lattices have been represented by standard reduced cells. By routinely calculating derivative supercells and subcells and matching against the file of known compounds, it is possible to find related materials and/or to make an identification in spite of certain types of errors made by the experimentalists (e.g. missing rows of spots on diffraction photographs or the diffractometer etc.). Finally, the identification obtained by lattice matching is verified using known chemical data. Practical experience and an analysis of the data in the NBS Crystal Data File have proved that the lattice-formula combination is highly characteristic of a crystalline material. Since the method is subject to precise mathematical techniques, the entire procedure can be highly automated. Both the unit-cell determination and the identification/characterization procedure can be carried out in the same instrument. A Fortran program and the NBS Crystal Data File are available.