On the Melting of Boron Chalcogenides B6S and B6Se under Pressure

Melting of new boron-rich chalcogenides, orthorhombic B6S and B6Se, has been studied at pressures up to 8 GPa using in situ electrical resistivity measurements. It was found that above 2.5 GPa both chalcogenides melt congruently, and the melting curves have a negative slope (‒61(5) K/GPa for B6S and –80(2) K/GPa for B6Se), indicating a higher density of the melts compared to the solid phases. The melting points at ambient pressure were estimated to be 2190(30) K for B6S and 2347(12) K for B6Se.