Polymorphic Transformations Under High Static Pressures

1 Polymorphic Transformations Under High Static Pressures 

Polymorphic transformations into the structure with Ac 8 were observed in cesium halides [71-74] atfollowing pressures CsCl 65, CsBr 53, Csl 39 GPa besides, Csl at P 200 GPa undergoes a smooth second-order transition into a hep structure with Ac = 12. Very peculiar transitions were observed in samarium chalcogenides SmX under high pressures the electron transition Sm(II) Sm(III) takes place with a sharp isomorphic decrease in the lattice parameters. Further compression leads to the transformation of the NaCl CsCl type. Values of pressures at the isomorphic (Pitr) and polymorphic (Pptr) transitions according to [75, 76] are following  

Compression of crystalline compounds MX2 leads to a consequential change in the structure types with an increase of density and coordination numbers (in 

T1O2 Si02 GeOz SnOz PbOz CrOz MnOz RuOz 

MgFz ZnFz MnFz FeFz CoFz NiFz PdFz  

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