Lattice dynamics of sodium superoxide

An extended three body force shell model (ETSM) has been applied for the prediction of lattice dynamics of orientationally disordered NaO2, by incorporating the effect of translational–rotational coupling between the translational modes and the orientation of superoxide O−2 molecules. The phonon dispersion curves (PDCs) computed from ETSM is generally, in good agreement with their available experimental data measured with the inelastic neutron scattering. The unusual feature is the upward curvature seen in transverse acoustic branch is more soft near the zone centre. We have also reported the cohesive, thermal and elastic properties of NaO2.