A non-empirical calculation of 2p core-electron excitation in compounds with 3d transition metal ions using...

Methodological advents for the calculation of the multiplet energy levels arising from multiple-open-shell 2p⁵3dⁿ⁺¹ electron configurations, with n = 0, 1, 2,… and 9, are presented. We use the Ligand-Field Density Functional Theory (LFDFT) program, which has been recently implemented in the Amsterdam Density Functional (ADF) program package. The methodology consists of calculating the electronic structure of a central metal ion together with its ligand coordination by means of the Density Functional Theory code. Besides, the core-hole effects are treated by incorporating many body effects and corrections via the configuration interaction algorithm within the active space of Kohn-Sham orbitals with dominant 2p and 3d characters of the transition metal ions, using an effective ligand-field Hamiltonian. The Slater-Condon integrals (F²(3d,3d), F⁴(3d,3d), G¹(2p,3d), G³(2p,3d) and F²(2p,3d)), spin-orbit coupling constants (ζ_2p and ζ_3d) and parameters of the ligand-field potential (represented within the Wybourne formalism) are therefore determined giving rise to the multiplet structures of systems with 3dⁿ and 2p⁵3dⁿ⁺¹ configurations. The oscillator strengths of the electric-dipole allowed 3dⁿ → 2p⁵3dⁿ⁺¹ transitions are also calculated allowing the theoretical simulation of the absorption spectra of the 2p core-electron excitation. This methodology is applied to transition metal ions in the series Sc²⁺, Ti²⁺,…, Ni²⁺ and Cu²⁺ but also to selective compounds, namely SrTiO₃ and MnF₂. The comparison with available experimental data is good. Therefore, a non-empirical ligand-field treatment of the 2p⁵3dⁿ⁺¹ configurations is established and available in the ADF program package illustrating the spectroscopic details of the 2p core-electron excitation that can be valuable in the further understanding and interpretation of the transition metal L_2,3-edge X-ray absorption spectra.