Differences in heavy metal nuclear momentum distributions (NMDs) in different metallic compounds due to chemical binding and effective temperature difference will most likely never be possible to be measured via conventional technique of recoil peak separation in neutron Compton scattering (NCS). However, in recent years a new avenue has been explored in the electron volt spectroscopy at ISIS, (n,gamma) absorption resonance Dopplerimetry (NRD). Following successful pilot work on caesium and iodine resonances, this proposal aims at extending the capability of NRD towards characterisation of compounds of a heavy resonant metal nucleus in the weak binding regime, tantalum (Ta), by comparing TaF3, TaCl3, TaN5O15 at T=10K, and TaH0.15 as a function of temperature. Obtained results will be compared with ab initio predictions obtained from CASTEP code.