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Haffner, Arthur; Weippert, Valentin; Johrendt, Dirk (2020): Polymorphism of Ba2SiP4. In: Zeitschrift für Anorganische und Allgemeine Chemie, Vol. 646, No. 3: pp. 120-124
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Abstract

The three‐dimensional SiP4 network in the known phosphidosilicate Ba2SiP4‐tI28 is analogous to β‐Cristobalite if oxygen is formally replaced by P–P dimers. Here we report a second polymorph Ba2SiP4‐oP56 [Pnma, a = 12.3710(4) Å, b = 14.6296(7) Å, c = 7.9783(3) Å; Z = 8] with chains of SiP4 tetrahedra connected by P–P bonds, reminiscent to the elusive fibrous SiO2. Ba2SiP4 is enantiotropic. The high temperature polymorph Ba2SiP4‐oP56 transforms to the low‐temperature phase Ba2SiP4‐tI28 at 650 °C and reconstructs to the high‐temperature modification at 1100 °C. DFT calculations predict an indirect optical bandgap of about 1.7 eV.