The Harmonic Picture of Nuclear Mean Kinetic Energies in Heavy Water

This paper presents a study of the total mean kinetic energy, hEKi, and of individual projections along a given molecular axis, hEKi ; for D and O nuclei in D2O, derived using a harmonic model. Our theoretical approach assumes decoupling amongst translational, rotational and vibrational modes. Resulting values of these dynamical quantities are discussed in terms of the anisotropy of the quantum kinetic energy tensor, its relation to the local potential, and deviations from the hypothesis of harmonicity and mode decoupling. Results are compared with corresponding quantities obtained from Deep Inelastic Neutron Scattering experiments performed on liquid and solid D2O, where the short-time dynamics and local environment of D and O atoms were probed. The present study con rms an overall picture where even small changes in the short-range environment of D and O nuclei have a strong in uence on the quantum behaviour of heavy water.