Guided by the above motto (quotation), we review a broad range of issues lying at the
foundations of Density Functional Theory, DFT, a theory which is currently omnipresent in …

Recent advances in reduced density matrix functional theory (RDMFT) and linear response
time-dependent reduced density matrix functional theory (TD-RDMFT) are reviewed. In …

The current work presents a new single-reference method for capturing at the same time the
static and dynamic electron correlation. The starting point is a determinant wave function …

Richardson–Gaudin (RG) states are employed as a variational wave function ansatz for
strongly correlated isomers of H4 and H10. In each case, a single RG state describes the …

The relative stability of the singlet, triplet, and quintet spin states of iron (II) porphyrin (FeP)
represents a challenging problem for electronic structure methods. While it is currently …

Eigenvectors of the reduced Bardeen–Cooper–Schrieffer (BCS) Hamiltonian, Richardson–
Gaudin (RG) states, are used as a variational wavefunction ansatz for strongly correlated …

In this work, we explore the use of Piris natural orbital functionals (PNOFs) to calculate
excited-state energies by coupling their reconstructed second-order reduced density matrix …

Does, or doesn't C2 break the glass ceiling of triple bonding? This work provides an
overview on the bonding conundrum in C2 and on the recent discussions regarding our …

The natural orbital functional (NOF) theory is briefly reviewed. The meaning of the top‐down
and bottom‐up approaches for the construction of a NOF is analyzed. A particular …

The cumulant expansion gives rise to an useful decomposition of the two‐matrix in which the
pair correlated matrix (cumulant) is disconnected from the antisymmetric product of the one …