High-pressure synthesis of a new calcium thioborate, CaB2S4

A new calcium thioborate, CaB2S4, was synthesized at high-pressure/temperature condition of 6.2 GPa and 800–1100 °C. The crystal structure was refined by the Rietveld method using powder X-ray diffraction data. The compound crystallizes into a cubic unit cell (a=11.210 Å, space group: Pa3), isostructural with a high-pressure polymorph of calcium borate, CaB2O4-IV. The unit cell consists of three-dimensional linkage of BS4-tetrahedra, and calcium atoms have coordination number of 12.