Answer to Question #120792 in Inorganic Chemistry for Yuki

Question #120792
GeO2 exists in a number of structures, most commonly a hexagonal form that is built on corner sharing GeO4 tetrahedra and a tetragonal structure in the mineral argutite built from edge sharing GeO6 octahedra.
Giving your reasoning predict if a direct transformation between the hexagonal and tetragonal structures is likely to be first order or continuous.
1
Expert's answer
2020-06-15T14:07:08-0400

The two polymorphs of "GeO_2" are hexagonal and tetragonal.

Hexagonal "GeO_2" has the same structure quartz , with germanium having coordination number "4" . Tetragonal "GeO_2" (The mineral argutite) has the notile-like structure seen in stishovite. Germanium in this motif has coordination number 6.

"GeO_2" is a chemical analogue of "SiO_2" . It is, to some extent a structural analogue, as the low and high-pressure short-range order (tetrahedral and octahedral) is the same. However, a number of differences exist. The "GeO_2" phase diagram, and all three "GeO_2" phases (crystalline, glass, liquid) have an increased sensitivity to pressure, undergoing pressure induced changes at much lower pressures than their equivalent "SiO_2" analogues.


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