Abstract :
The Chevrel-phase pseudo-binary solid solution Mo6Se8–Mo6Te8 was studied by the room-temperature solid-state 95Mo NMR spectroscopy. The experimental spectra were fitted by an anisotropic central line of axial symmetry corresponding to the molybdenum atoms of the Mo6 metallic cluster, while a gaussian line of smaller intensity could be due to some residual molybdenum powder. Quadrupolar effects due to the chalcogen network were neglected since the shape and width of the resonant line (+1/2→−1/2 transition) are shown to be independent of the chalcogen substitution. Analysis of the anisotropy of the Knight shift leads us to conclude about the importance of the Mo (x2−y2) molecular orbitals, in contrast to the z2 contribution which controls the Mo–X dipolar interactions. The Knight shift varies linearly with the Se/Te ratio and it was found to be proportional to the room-temperature susceptibility, implying the existence of polarization mechanisms between d and s electron spins.
