GERMANIUM. XXXIX. THE POLYMORPHISM OF GERMANIUM DIOXIDE¹

Abstract

This article is based upon the thesis presented to the Faculty of the Graduate School of Cornell University by D. S. Morton in partial fulfilment of the requirements for the degree of Doctor of Philosophy.2 Goldschmidt, Naturwissenschaften, 14, 295 (1926).

Infrared studies on polymorphs of silicon dioxide and germanium dioxide

“…This difference is due to the markedly different Ge-O bond length and bond energy for t he two forms. For tetragonal Ge0 2, the Ge-O bond length [3] is 1.86 A. The bond length for the h exagonal Ge02 has not been given, but it is likely that i t is shorter than 1.86 A, corresponding to a stronger bond and larger bondstretching force constant and vibrational frequency.…”

“…Because coordination of silicon in coe ite [2] has not been established, one of the objectives of this work was to furnish evidence for either the fourfold coordination of the other polymorphs of Si02 or for a different coordination. I n the tetragonal form of Ge02 the germanium atom has a sixfold coordination with oxygen, whereas in the quartz-type hexagonal Ge0 2 the germanium atom has the fourfold coordination of silicon in quartz [3,4]. A similar tetragonal form of silica is not known but has been predicted by analogy with germania.…”

The crystal structure of quartz-like GeO2

“…One modification is of the a-quartz type (Zaehariasen, 1928) and thus has 4:2 coordination; the other form, of the futile type (Laubengayer & Morton, 1932), accordingly has 6:3 coordination. These latter investigators have shown quartz-like GeOe to be actually the stable high-temperature phase.…”

Optical properties of germanium dioxide in the rutile structure

“…GeO 2 crystallizes with the bulk rutile structure (space group P4 2 /mnm) [2,19,20]. In Figure 1 a schematic representation of the lattice is depicted.…”

“…GeO 2 occurs in three stable forms at ambient temperature [1]. The first form has the rutile tetragonal structure (P4 2 /mnm) with octahedral coordination [2]. The second form has the trigonal structure of α-quartz [3], with tetrahedral coordination.…”