Ammonium, potassium, rubidium and cesium hexavanadates

The following anhydrous alkali hexavanadates have been prepared and shown to be isostructural: K2V6O16, (NH4)2V6O16, Rb2V6O16 and Cs2V6O16. They are monoclinic and contain six vanadium atoms per unit cell. The crystal lattice undergoes a linear expansion in the a and e dimensions as the ionic radius of the cation increases. The hexavanadates of lithium and sodium could not be prepared.