Systematic of polymorphous transformation of crystals, generalized on the base of M. J. Burger’s criteria

Filatov S.K., Paufler P.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2019. V. 148. N 5. P. 1-23

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Language: Russian 


The paper proposes an extended (3 × 3) classification of polymorphous transformations, which includes the 0th coordination sphere in addition to the M. J. Burger’s I and II coordination spheres. As a result, the first parameter of this classification is the number of a transformable coordination sphere — it takes the value equal to 0 (atom, ion), 1 (the coordination polyhedra) and 2 (the nearest to the coordination polyhedra environment). The second parameter of the classification is determined by the Burger’s energy barrier for a transformation. And here, in addition to transformations with a break of chemical bonds (reconstructive) and without it (deformational), some intermediate types of transformations take place — with a disordering of structural units (atoms, molecules and other atomic complexes). As examples of polymorphous transformations with transformation of the 0th coordination sphere, there are considered electron transitions in an atom, changes of the atom’s spin, and magnetic ordering of atoms in a crystal structure. Transformations with disordering are illustrated by substitutions-jumps of structural units and their slowed down or free rotation. There is developing the concept of “polymorphism” of chemical elements.

Key words: polymorphism in crystals, classification of polymorphous transformations, crystal structure