Dislocations in α-sulphur

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Abstract
A study has been made of the solvent etching of naturally-occurring (001), (011), {111} and {113} faces and prepared (110) faces of orthorhombic sulphur crystals grown from solution in carbon disulphide. No pitting was observed on the (011) and {113} faces. Etching of the remaining faces revealed crystallographically-shaped pits, the shapes and distributions of which were consistent with their formation at the emergent ends of dislocations in the lattice. The probable geometry of the dislocations is discussed. Deformation by point indentation indicated that slip occurs predominantly on {111} glide planes. An X-ray topographic study is also reported, which complements the above results. Direct evidence is presented on the geometry of the active slip systems and on the mobility of individual dislocations. Of the observed slip systems it is shown that only (1 1) [110], ( 11) [110], (111) [11 0], (11 ) [1 0] are facile; {111} 〈10 〉 or 〈0 1〉 and (001) [100] or 〈1 0〉 are much more difficult to activate. The existence of only four facile slip systems is consistent with the brittle nature of these crystals.