C. Guidotti

SCF‐MO's and Molecular Properties of Methane

SCF‐MOs of the CH4 molecule have been calculated for the experimental geometry by using bases of up to 39 STOs. The best molecular energy obtained is −40.20452 a.u. The ground‐state wavefunctions have been utilized to compute some one‐electron properties, viz., the electric octupole moment, the electric field gradient at the protons, and the diamagnetic susceptibility. In addition, the electric polarizability and the paramagnetic susceptibility have been evaluated using a perturbed H–F calculation.

SCF MO's and Molecular Properties of H2O

SCF MOs of H2O molecule have been calculated for a geometry very close to the experimental one, using a basis set of 29 STOs. The evaluated HF energy is −76.0384 a.u. Several ground‐state one‐electron properties have also been computed, viz., the first three electric multipole moments, electric field and gradient field at the nuclei, electric polarizability, and magnetic susceptibility.

Electric and magnetic properties of N2 and H2O by the equations‐of‐motion method

Dynamic multipole polarizabilities and the magnetic dipole susceptibility of N2 and H2O are evaluated in the framework of the equation‐of‐motion method corresponding to the random phase (RPA) and Tamm–Dancoff approximations (TDA). The results are presented in the form of a Cauchy expansion truncated after the ω4 terms. Nuclear magnetic shielding constants of N, H, and O are obtained as by products of the main calculations. While the RPA results for the magnetic properties compare very well with available experimental data, the computed values for the electric observables are only in moderately good agreement with the experiments, suggesting an inadequacy of the employed basis sets and a different relevance of the correlation effects as well. The dipole–dipole van der Waals dispersion coefficients for the pairs N2–N2, H2O–H2O, and N2–H2O obtained by RPA values of the dipole polarizability at imaginary arguments compare only approximately well with semiempirical estimates.

Experimental and TDDFT Characterization of the Light-Induced Cluster-to-Iron Charge Transfer in the (Ferrocenylethynyl)-Substituted Trinuclear Platinum Derivative [Pt3(μ-PBut2)3(CO)2(C≡C−Fc)]+

The reaction between Pt(3)(mu-PBu(t)(2))(3)(CO)(2)Cl (2) and ethynylferrocene, in the presence of catalytic amounts of CuI, gives Pt(3)(mu-PBu(t)(2))(3)(CO)(2)C[triple bond]CFc (1), characterized by X-ray crystallography and representing a rare example of the sigma-coordination of an alkynyl moiety to a cluster unit. In a dichloromethane (CH(2)Cl(2)) solution, compound 1 undergoes three consecutive one-electron oxidations, the first of which is assigned to the ferrocene-centered Fe(II)/Fe(III) redox couple. Spectroelectrochemistry, carried out on a solution of 1, shows the presence of a broad band in the near-IR region, growing after the electrochemical oxidation, preliminarily associated with a metal-to-metal charge transfer toward the Fe(III) ion of the ferrocenium unit. Density functional theory (DFT) has been employed to analyze the ground- and excited-state properties of 1 and 1(+), both in the gas phase and in a CH(2)Cl(2) solution. Vertical excitation energies have been computed by the B3LYP hybrid functional in the framework of the time-dependent DFT approach, and the polarizable continuum model has been used to assess the solvent effect. Our results show that taking into account the medium effects together with the choice of an appropriate molecular model is crucial to correctly reproducing the excitation spectra of such compounds. Indeed, the nature of the substituents on P atoms has been revealed to have a key role in the quality of the calculated spectra.

More on the quantum propagator of a particle in a linear potential

The construction of the exact quantum propagator of a particle subjected to a constant force offers a challenge to existing propagator methodology. Here, besides considering the traditional approach, which involves an expansion in the complete set of energy eigenstates, we illustrate (i) the merits of a rather more elegant procedure founded on the ‘‘disentanglement’’ of the time‐evolution operator and (ii) the power of a general treatment based on a time‐dependent variational approach.

SCF MO's and Molecular Properties of Methyl Fluoride

The SCF MOs of CH3F have been calculated by using bases of up to 47 STOs. The best molecular energy obtained is − 139.0612 a.u. The ground‐state wavefunctions have been utilized to compute several observables corresponding to one‐electron operators, viz., the electric dipole, quadrupole, and octopole moments, the electric field gradient at the carbon atom and at the proton, and the diamagnetic part of the susceptibility. In addition, by using the coupled HF perturbation theory, the electric polarizability and the paramagnetic part of the susceptibility have been computed.

Long-range interaction energy of two- and four-electron atoms☆

Abstract The first three long-range dispersion coefficients C 6 , C 8 and C 10 for all the pairs of atoms which arise from the iso- electronic sequences HeC 4+ , BeC 2+ have been obtained by coupled time-dependent Hartree—Fock theory. In addi- tion, some comparisons with other more approximate schemes contained in that method have been carried out

Inelastic scattering of fast electrons from molecular systems. I. Hydrogen molecule

Abstract Inelastic scattering of fast electron from the electronic ground state of the H 2 molecule is investigated within the first Born approximation. The relevant transition properties have been obtained in some approximation corresponding so ??? order solutions of the equations-of-motion formation put forward by Rowe-Tamm-???approximation, random phase approximation. Generalized oscillator strengths and ??? of different symmetry are evaluated and discussed.

Some spectroscopic properties of gold nanorods according to a schematic quantum model founded on the dielectric behavior of the electron-gas confined in a box. I

Abstract The long-standing confined-electron-gas approach employed for simulating in a simple way the size-dependent “free electron” dielectric behavior of isotropic nanoparticles has been extended to the investigation of some spectroscopic properties of gold nanorods. The model adopted takes also into accounts size-independent interband effects estimated in a semiempirical way from bulk dielectric data. Predictions relative to the optical absorption and photoluminescence behavior, associated with the coherent, collective excitation of the electron gas, are derived on the basis of a fairly simple formalism, whose implementation allows to deal with a number of conduction electrons of the order of ca. 10 4 , at a tolerable computational cost. The predictions of the model agree reasonably well with the few available experimental data. The nature of some approximations introduced suggests also the opportunity of a further analysis of specific points.

LONG-RANGE INTERACTIONS AMONG He AND Be ATOMS.

Long‐range dispersion energies for the atom pairs He–He, He–Be, and Be–Be in their ground states have been calculated in the form E disp=C6/R6+C8/R8+C10/R10+C11/R11+C12/R12, the coefficients Cn being obtained from the appropriate dynamic polarizabilities at imaginary frequencies. The needed polarizabilities of imaginary argument have been calculated within the time‐dependent coupled Hartree‐Fock approximation. Three‐body nonadditive contributions to the interaction energies have been also evaluated.