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E Sicilia

Publications and source records attributed to E Sicilia.

8 recordsLinked to original sources
PubMed2006

LANL2DZ basis sets recontracted in the framework of density functional theory.

In this paper we report recontracted LANL2DZ basis sets for first-row transition metals. The valence-electron shell basis functions were recontracted using the PWP86 generalized gradient approximation functional and the hybrid B3LYP one. Starting from the original LANL2DZ basis sets a cyclic method was used in order to optimize variationally the contraction coefficients, while the contraction scheme was held fixed at the original one of the LANL2DZ basis functions. The performance of the recontracted basis sets was analyzed by direct comparison between calculated and experimental excitation and ionization energies. Results reported here compared with those obtained using the original basis sets show clearly an improvement in the reproduction of the corresponding experimental gaps.

Journal Article↗
PubMed2005

Newly developed basis sets for density functional calculations.

Optimized contracted Gaussian basis sets of double-zeta valence polarized (DZVP) quality for first-row transition metals are presented. The DZVP functions were optimized using the PWP86 generalized gradient approximation (GGA) functional and the B3LYP hybrid functional. For a careful analysis of the basis sets performance the transition metal atoms and cations excitation energies were calculated and compared with the experimental ones. The calculated values were also compared with those obtained using the previously available DZVP basis sets developed at the local-density functional level. Because the new basis sets work better than the previous ones, possible reasons of this behavior are analyzed. The newly developed basis sets also provide a good estimation of other atomic properties such as ionization energies.

Journal Article↗
PubMed2002

On the hardness evaluation in solvent for neutral and charged systems.

The influence of water on the hardness values of a series of neutral and charged molecules has been studied in the framework of density functional theory using the polarizable continuum model to take into account solvent effects. Three working formulas already widely tested in gas-phase have been used and the results compared. Two of the methods employed going from gas phase to solvent phase give values that do not change, while the results of the third method show remarkable changes. To check the reliability of the hardness behavior found, a test based on the hard-soft/acid-base principle and the calculation of the free energy of reaction has been applied using the adopted procedures.

Journal Article↗
PubMed2001

Reaction of SC+(1D,3D) with H2O, NH3, and CH4: a density functional study.

Density Functional Theory has been used to explore quantitative details of the potential energy hypersurface for the insertion reaction of scandium ion into the O-H, N-H, and C-H bond of water, ammonia, and methane molecules leading to H2 elimination. Both singlet and triplet state channels have been considered. On the basis of the obtained results, it is possible to conclude that for the molecules considered the reaction is a spin-forbidden process. Indeed, it starts in the triplet ground state and ends in the singlet state, the change of the spin state probably occurring immediately after the formation of the electrostatic complex intermediate.

Journal Article↗
PubMed1990

[Chordoma of the base of the skull. A case report].

Chordomas of the skull base are neoplasms derived from persistent embryologic remnants. In spite of its histologic classification as benign tumors, the site and the adverse possibilities of the management its behaviour is malignant like. The case here referred to was localized in the basioccipital region and protruded in the rhinopharynx. Perusal of the bibliography and prognostic assessment of these type of patients.

Chordoma↗
PubMed1990

[Lingual hamartoma].

The hamartoma is a benign tumor resulting of a mixture of normal and mature tissues and cells, sitting on an organ or tissue showing identical cell components. From the perusal done of the bibliography they appear as rare malformations basically compound of fibrous tissue, fat, acini of salivary glands and smooth muscle.

Aged↗