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

https://doi.org/10.30695/zrmo/2019.1485.00

Full text is available on Journals.eco-vector.com

Language: Russian

Abstract

The paper proposes an extended (3 × 3) classification of polymorphous transformations, which includes the 0^th 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 0^th 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