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A closed local-orbital unified description of DFT and many-body effects

2022; IOP Publishing; Volume: 34; Issue: 30 Linguagem: Inglês

10.1088/1361-648x/ac6eae

1361-648X

F. Florès, Diego Soler‐Polo, José Ortega,

Inorganic Chemistry and Materials

Density functional theory (DFT) is usually formulated in terms of the electron density as a function of positionn(r). Here we discuss an alternative formulation of DFT in terms of the orbital occupation numbers {nα} associated with a local-orbital orthonormal basis set {ϕα}. First, we discuss how the building blocks of DFT, namely the Hohenberg-Kohn theorems, the Levy-Lieb approach and the Kohn-Sham method, can be adapted for a description in terms of {nα}. In particular, the total energy is now a function of {nα},E[{nα}], and a Kohn-Sham-like Hamiltonian is derived introducing the effects of the electron-electron interactions via effective potentials,{Vαeff=∂Eee[{nβ}]/∂nα}. In a second step we consider the Hartree and exchange energies and discuss how to describe them, in the spirit of a DFT approach, in terms of the orbital occupation numbers. In this contribution special attention is paid to the description of the (intra-atomic) correlation energy and corresponding correlation potentials {Vcorr,α}. For this purpose, a model system is analyzed in detail, whereby an atomic Hamiltonian interacts with the environment via a simplified model; the use of this model allows us to obtain the correlation energy and potentials (in terms of {nα}) for different cases corresponding to low, intermediate and high electron correlations.