Lattice Matching (LM)—Prevention of Inadvertent Duplicate Publications of Crystal Structures
Lattice-matching techniques have proved to be extremely effective for the identification of unknown crystalline materials. A commonly employed lattice-matching strategy is based on matching the reduced cell of an unknown against a database of known materials represented by their respective standard reduced cells. The success of the method relies on the fact that the lattice or the lattice plus chemical information (e.g., element types) is highly characteristic of a material—like a fingerprint. Because of its intrinsic power, the procedure has many and diverse applications—in materials characterization, in nano-technology, in epitaxial growth, in materials design, etc. An especially fruitful role for the method is in the journal publication process as the quality of the scientific literature can be enhanced. The focus herein is on the major role that lattice matching can play in the prevention of inadvertent duplicate publications of the same structure and in the determination of key cross-references.
The reduced cell: its use in the identification of crystalline materials
A rapid-identification file for crystalline materials is being prepared from the Crystal Data file. In this new file, each cell is represented in its reduced form, which is unique, primitive, and based on the three shortest noncoplanar vectors of the lattice. Unknown materials can be rapidly matched with the same or related crystals in the file. To identify an unknown crystalline material, a primitive cell is first determined experimentally, then it is reduced and checked against the file for a match. Even if the cell of the unknown lattice is not primitive, identification is still possible by calculating appropriate derivative lattices, reducing them, and then checking the file.
A magic-angle spinning 31P NMR investigation of crystalline and glassy inorganic phosphates
31NMR spectra of several inorganic phosphates have been examined both in the crystalline and the glassy states. The parameter (Zeff/r)q clearly demarcates ortho-, pyro- and meta-phosphates in terms of the 31P chemical shifts. Based on such a diagram, inorganic phosphate glasses are found to consist essentially of metaphosphate units. NMR resonance of the glasses are generally much broader than those of crystalline phosphates.