Abstract:
This paper presents an experimental measurement of the electronic structure of
Na2O in the solid phase using electron momentum spectroscopy (EMS) and compares the
results with ab initio calculations performed within the linear combination of atomic orbitals
approximation (LCAO). While Hartree-Fock (HF) can reproduce elastic properties we find it
overestimates splitting of the oxygen valence bands by around 30 % and the width of the O 2p
band by a factor of 2. Our experimental values are 15.85 ± 0.2 eV and 0.6 ± 0.2 eV for these
two quantities respectively. Density Functional (DFT) methods are significantly better, with
the hybrid functional PBE0 predicting the oxygen band gap to within the experimental error.
PBE0 also gives the best estimate of the Na core level energies. In contrast, HF performs best
for the splitting between the oxygen and sodium bands. Our experimental values of 32.85 ±
0.2 eV and 27.45 ± 0.2 eV for the Na 2p-Na 2s and O 2p-Na 2p splittings agree well with
previous measurements. Distribution of electron density both within the bands and between
the bands is not reproduced by any of the computational methods employed.
