Polytypes and Twins in New Boron-Rich Chalcogenides B6S and B6Se Synthesized at High Pressure

Microstructure of new boron-rich chalcogenides, orthorhombic B6X (X = S, Se) synthesized at high pressures and high temperatures, has been studied by high-resolution transmission electron microscopy. Two twins systems have been found along planes (101) and (002). Apart from numerous twins on the (101) plane, two types of polytypes were found: ABAB in both chalcogenides and AB1CD1AB1CD1 in B6Se. It has been shown that shear bands in B6S and cracks in both materials lie in planes {011}.