Structure
The forms of germanium dioxide to an extent parallel those of silicon dioxide. Hexagonal GeO2 has the same structure as β-quartz (germanium having coordination number 4); tetragonal GeO2 (the mineral argutite) has the rutile-like structure of stishovite (germanium having coordination number 6); and amorphous (glassy) GeO2 is similar to fused silica.
Germanium dioxide can be prepared in both crystalline and amorphous forms. At ambient pressure the amorphous structure is formed by a network of GeO4 tetrahedra. At elevated pressure up to approximately 9 GPa the germanium average coordination number steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance. At higher pressures, up to approximately 15 GPa, the germanium coordination number increases to 6 and the dense network structure is composed of GeO6 octahedra. When the pressure is subsequently reduced, the structure reverts back to the tetrahedral form. At high pressure, the rutile form converts to an orthorhombic CaCl2 form.
Read more about this topic: Germanium Dioxide
Famous quotes containing the word structure:
“Each structure and institution here was so primitive that you could at once refer it to its source; but our buildings commonly suggest neither their origin nor their purpose.”
—Henry David Thoreau (1817–1862)
“If rightly made, a boat would be a sort of amphibious animal, a creature of two elements, related by one half its structure to some swift and shapely fish, and by the other to some strong-winged and graceful bird.”
—Henry David Thoreau (1817–1862)
“The verbal poetical texture of Shakespeare is the greatest the world has known, and is immensely superior to the structure of his plays as plays. With Shakespeare it is the metaphor that is the thing, not the play.”
—Vladimir Nabokov (1899–1977)