STRUCTURES OF IV GROUP ELEMENTS AND SOLID PHASES OF WATER
G.G. Malenkov
Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
Keywords: полиморфизм, лед, углерод, кремний, германий, олово, кристаллические структуры, аморфные тела, клатратные соединения, polymorphism, ice, carbon, silicon, germanium, tin, crystal structures, amorphous bodies, clathrate compounds
Abstract
The structures of solid phases of water and IV(b) group elements of the periodic table (carbon, silicon, germanium, and tin) are compared. Both water and mentioned elements are characterized by high polymorphism. All mentioned elements and ice have a modification with a diamond structure. For all substances considered, except tin, modifications with the structure of a hexagonal analogue of diamond (lonsdaleite) have been known. The modification with the β-Sn structure has not been known only for ice and carbon. One of the germanium modifications is isostructural to ice III. Tin has a modification with the α-Fe structure. The same structure is observed for ices VII, VIII, and X. Both water and IVb group elements can form clathrate hydrates with cavities in the form of Allen's polyhedra. In water clathrates these cavities contain noble gas atoms (Ar, Kr, Xe) and various molecules. Clathrates of IVb group elements contain metal atoms as well as noble gas atoms.
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