Abstract
The commensurate state of 4Hb-TaSe2 has been studied at room temperature by X-ray single-crystal diffraction methods. The in-plane Ta atomic displacements have been determined. It is shown that clusters of 13 Ta atoms can be isolated and correspond to an attractive interaction between metal atoms. Correspondingly, the Ta-Ta interatomic distances range from about 3·26 to 3·86 A. We also find, at least in bulk materials, that the two twin-related layer variants, α and β, are not completely stacked at random as suggested by previous electron diffraction experiments and by consideration of trigonal prismatic sandwich screening.