Low energy excitations in NiO based on a direct Δ-SCF approach

• Published in: Journal of physics. Condensed matter 2018-12, Vol.30 (49), p.495901-495901
• Main Authors: Mackrodt, William C, Salustro, Simone, Civalleri, Bartolomeo, Dovesi, Roberto
• Format: Article
• Language: English
• Subjects: excitation; NiO; Δ-SCF
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/1361-648X/aaea5d

This paper reports calculated energies and electronic structures of nineteen excited states in NiO based on a Δ-SCF approach reported previously for the transitions in NiO and Sr2CuO2Cl2. They are the spin-flip: ; eight : (one electron) 3A2g  →  3T2g, (two electron) 3A2g  →  3T1g, 3A2g  →  a1Eg, 3A2g  →  1T2g, 3A2g  →  1T1g, 3A2g  →  b1Eg, 3A2g  →  b1T2g; two O(2p)  →  Ni(3d); seven Ni(3d)  →  O(2p) (including two spin-flip) and the O(2s)  →  Ni(3d) charge transfer excitations, which span an energy range from 0.25 eV to 17.53 eV, and include the fundamental band gap associated with an excitonic O(2p)  →  Ni(3d) transition at 4.23 eV. These are compared to absorption and emission spectra, and previous calculations. In the case of the O(2p)  →  Ni(3d) excitations, comparisons are given for gap and Γ-point energies derived from HF, PBE0, HSE06, B3LYP, B1WC, GGA and LDA one-electron approximations. Finally, the directly calculated Stokes shifts and associated luminescence energies for the two O(2p)  →  Ni(3d) transitions are reported, where the excitonic value is found to be in good agreement with the recently reported experimental value.