The piloting experiments RB820478, RB610497 and RB 10067 on VESUVIO on (NH4)2PdCl6 and (NH4)2TeCl6 have shown that: (i) at 300 K, the dynamics of NH4+ and PdCl6- and TeCl6- is fully decoupled, (ii) H momentum distribution is non-Gaussian. A classical onset exists for both compounds: At 50K both undergo a transition from quantum tunnelling to stochastic motion despite tunnelling frequencies in both substances differing three orders of magnitude. We will look at this classical onset of H/D dynamics in (NH4)2PdCl6/(ND4)2PdCl6 and (NH4)2TeCl6. We will obtain information on proton/deuteron harmonic, anharmonic and stochastic motions and potential barriers associated as well as characteristic scale of motions from the form factors. Localized and translational modes will be measured vs. momentum transfer at 30, 40, 50, 60 and 70 K and at 300K. Ab intio PW-DFT (CASTEP) will be performed.