Transformation of threedimensional threeconnected silicon nets in SrSi _{2}
Abstract
Dimorphic SrSi _{2} is the first compound for which the two simplest threedimensional threeconnected nets are found in its polymorphs. The cubic net of threeconnected silicon atoms (SrSi _{2} type of structure) can be transformed into the tetragonal one (αThSi _{2} type of structure) by a highpressurehightemperature treatment. The tetragonal phase is quenchable. Heating of this phase to 600700°C at ambient pressure results in transformation into the cubic one. At a heating rate of 20°C/min complete transformation can be achieved within 5 min in a DTA apparatus. The energy of transformation has been obtained from the peak areas of the DTA curves to 1.6 ± 0.3 kcal/mole. Although the transformation between the threedimensional threeconnected sets in SrSi _{2} must be formally classified as a reconstructive one, a relatively small entropy change ( ∆S = 1 · _{1} cal/deg · mole) has been calculated from the change in molar volume and pT equilibrium conditions. Therefore, structural relations between the cubic and the tetragonal nets are discussed.
 Publication:

Journal of Solid State Chemistry France
 Pub Date:
 March 1978
 DOI:
 10.1016/00224596(78)900105
 Bibcode:
 1978JSSCh..24..199E