Entanglement and Mutual Information in Molecules: Comparing Localized and Delocalized Orbitals.

The use of the mutual information (MI) as a measure of the entanglement in quantum systems has gained a consensus in recent years, even if there is an ongoing effort to distinguish the classical and quantum contributions contained therein. This quantity has been first introduced in condensed matter physics, in particular, in studies based on the density matrix renormalization group method. This method has been successfully adapted to quantum chemistry problems, opening the way to compute MI also in molecular systems.

Computation of the Isotropic Hyperfine Coupling Constant: Efficiency and Insights from a New Approach Based on Wave Function Theory.

The present paper reports an original computational strategy for the computation of the isotropic hyperfine coupling constants (hcc). The algorithm proposed here is based on an approach recently introduced by some of the authors, namely, the first-order breathing orbital self-consistent field (FOBO-SCF). The approach is an almost parameter-free wave function method capable to accurately treat the spin delocalization together with the spin polarization effects while staying in a restricted formalism and avoiding spin contamination.

The "Fermi hole" and the correlation introduced by the symmetrization or the anti-symmetrization of the wave function.

The impact of the antisymmetrization is often addressed as a local property of the many-electron wave function, namely that the wave function should vanish when two electrons with parallel spins are in the same position in space. In this paper, we emphasize that this presentation is unduly restrictive: we illustrate the strong non-local character of the antisymmetrization principle, together with the fact that it is a matter of spin symmetry rather than spin parallelism. To this aim, we focus our attention on the simplest representation of various states of two-electron systems, both in atomic (helium atom) and molecular (H and the π system of the ethylene molecule) cases.

Highly efficient perturbative + variational strategy based on orthogonal valence bond theory for the evaluation of magnetic coupling constants. Application to the trinuclear Cu(ii) site of multicopper oxidases.

A new strategy based on orthogonal valence-bond analysis of the wave function combined with intermediate Hamiltonian theory has been applied to the evaluation of the magnetic coupling constants in two AF systems. This approach provides both a quantitative estimate of the J value and a detailed analysis of the main physical mechanisms controlling the coupling, using a combined perturbative + variational scheme. The procedure requires a selection of the dominant excitations to be treated variationally.

Beryllium dimer: a bond based on non-dynamical correlation.

The bond nature in beryllium dimer has been theoretically investigated using high-level ab initio methods. A series of ANO basis sets of increasing quality, going from sp to spdf ghi contractions, has been employed, combined with HF, CAS-SCF, CISD, and MRCI calculations with several different active spaces. The quality of these calculations has been checked by comparing the results with valence Full-CI calculations, performed with the same basis sets.

[Radiological study of non-neoplastic renal expansive processes (author's transl)].

The radiological aspects of non-neoplastic renal expansive processes are reviewed and discussed, particular attention being paid to indications for the various investigation techniques and differential diagnosis. Numerous examples are reported.

[Selective arteriography of the carotid and vertebral arteries by the femoral route: review of 225 patients (author's transl)].

Selective arteriography of the carotid and vertebral arteries by the femoral route was carried out in 225 cases. The technique, results, indications and contraindications are reported and discussed together with complications.

[Radiological study of the neoplastic bladder].

Radiological methods useful in the examination of bladder tumours are reviewed, with particular reference to preoperative evaluation in accordance with the system. Examples are drawn from a personal series.