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Spin-polarized density functional theory is used to analyze chemical reactivity from a more general point of view, which distinguishes between the changes produced by charge transfer between the interacting species (changes in the total number of electrons, N = + TVj where f refers to spin-up or a and , to spin-down or ß) and the changes produced by the redistribution of the electronic density of each of the interacting species (changes in the spin number, Ns = Af -7V|). It is found that the response of the system to changes in N and the external potential is given in terms of the chemical potential, the hardness, the electronic density, and the Fukui function, while the response of the system to changes in 7VS and an external magnetic field is given in terms of a new set of parameters which we have named the spin potential, the spin hardness, the spin density, and the spin Fukui function. Making use of the Kohn-Sham approach to density functional theory, it is shown that the generalized Fukui functions can be reduced to a set of spin-polarized classical frontier orbitals by imposing frozen core approximations.

The lifetime of a resonance state overlapping with a second resonance is shown to be strongly enhanced (by a factor of 3) by combining two pump pulses to simultaneously excite the two resonances. Such an enhancement is produced by interference effects occurring between the two coherently excited overlapping resonances. A high degree of control on the intensity of interference, and thus on the resonance lifetime enhancement, is found to be achieved by varying the delay time between the pulses and their relative intensities.

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The derivations that lead to the introduction of the electrophilicity and of the electrodonating and electroaccepting powers are revisited. Special emphasis is given to the role played by the chemical potential of the bath in the definition of these global reactivity indexes. An alternative explanation to the increase of the energy when the system donates electrons is provided. It is also shown that the 2-parabolas model correctly predicts that there is no electron flow when the chemical potential of the bath, μ, is in the interval μ^- < μ < μ⁺, in almost complete consonance with the ensemble theorem at 0 K. The electrodonating and electroaccepting powers of neutral atoms in the Periodic Table are evaluated and used to explain how the values of these indexes will distribute in the electrodonating-electroaccepting powers plane.

We summarize our contributions on the quest of new planar tetracoordinate carbon entities (new carbon molecules with exotic chemical structures and strange bonding schemes). We give special emphasis on the rationalization why in this type of molecules the planar configuration is favored over the tetrahedral one. We will concentrate on the latter and will show that molecules containing planar tetracoordinate carbons have a stabilizing system of delocalized electrons, which shows similar properties as systems in aromatic molecules.

In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The format of the paper is that of a roundtable discussion, in which the participants express and exchange views on DFT in the form of 300 individual contributions, formulated as responses to a preset list of 26 questions. Supported by a bibliography of 776 entries, the paper represents a broad snapshot of DFT, anno 2022.

Natural orbital functional theory is considered for systems with one or more unpaired electrons. An extension of the Piris natural orbital functional (PNOF) based on electron pairing approach is presented, specifically, we extend the independent pair model, PNOF5, and the interactive pair model PNOF7 to describe spin-uncompensated systems. An explicit form for the two-electron cumulant of high-spin cases is only taken into account, so that singly occupied orbitals with the same spin are solely considered. The rest of electron pairs with opposite spins remain paired. The reconstructed two-particle reduced density matrix fulfills certain N-representability necessary conditions, as well as guarantees the conservation of the total spin. The theory is applied to model systems with strong non-dynamic (static) electron correlation, namely, the one-dimensional Hubbard model with periodic boundary conditions and hydrogen rings. For the latter, PNOF7 compares well with exact diagonalization results so the model presented here is able to provide a correct description of the strong-correlation effects.