Aldo Amore Bonapasta

Reaction Pathways for Oxygen Evolution Promoted by Cobalt Catalyst

The in-depth understanding of the molecular mechanisms regulating the water oxidation catalysis is of key relevance for the rationalization and the design of efficient oxygen evolution catalysts based on earth-abundant transition metals. Performing ab initio DFT+U molecular dynamics calculations of cluster models in explicit water solution, we provide insight into the pathways for oxygen evolution of a cobalt-based catalyst (CoCat). The fast motion of protons at the CoCat/water interface and the occurrence of cubane-like Co-oxo units at the catalyst boundaries are the keys to unlock the fast formation of O-O bonds. Along the resulting pathways, we identified the formation of Co(IV)-oxyl species as the driving ingredient for the activation of the catalytic mechanism, followed by their geminal coupling with O atoms coordinated by the same Co. Concurrent nucleophilic attack of water molecules coming directly from the water solution is discouraged by high activation barriers. The achieved results suggest also interesting similarities between the CoCat and the Mn4Ca-oxo oxygen evolving complex of photosystem II.

Local structure of (Ga,Fe)N and (Ga,Fe)N:Si investigated by x-ray absorption fine structure spectroscopy

X-ray absorption fine-structure (XAFS) measurements supported by ab initio computations within the density functional theory (DFT) are employed to systematically characterize Fe-doped as well as Fe- and Si-codoped films grown by metalorganic vapor-phase epitaxy. The analysis of extended-XAFS data shows that depending on the growth conditions, Fe atoms either occupy Ga substitutional sites in GaN or precipitate in the form of

A hybrid zinc phthalocyanine/zinc oxide system for photovoltaic devices: a DFT and TDDFPT theoretical investigation

ϵ{text{-Fe}}_{3}text{N}

Molecular cluster studies of the crystal growth process in mbe and mo-mbe: i. structure and thermodynamics of gas phase reactants [as2, as4, ga(ch3)3]

nanocrystals, which are ferromagnetic and metallic according to the DFT results. Precipitation can be hampered by reducing the Fe content, by increasing the growth rate, or by codoping with Si. The near-edge region of the XAFS spectra provides information on the Fe charge state and shows its partial reduction from

The effect of Co doping on the conductive properties of ferromagnetic ZnxCo1−xO films

{text{Fe}}^{+3}

Competition between electron-donor and electron-acceptor substituents in nitrotoluene isomers: a photoelectron spectroscopy and ab initio investigation

to

Molecular cluster studies of defects in tetrahedral lattices: Dangling bonds reconstruction at the core of a 90° partial dislocation in diamond

{text{Fe}}^{+2}

Unexpected Rotamerism at the Origin of a Chessboard Supramolecular Assembly of Ruthenium Phthalocyanine

upon Si codoping, in agreement with the Fe electronic configurations expected within various implementations of DFT.

XAS, XES and DFT simulations to bridge local and macroscopic properties in GaAsN

By combining ab initio density functional theory (DFT) and time-dependent density functional perturbation theory (TDDFPT) methods, we investigate the structural, electronic and optical properties of a zinc phthalocyanine (ZnPc) molecule interacting with the zinc oxide (ZnO) wurtzite (100) surface. Our results reveal the existence of a strong molecule–surface coupling whose major effect is the appearance of a new unoccupied electronic level, deriving from an intimate mixing of ZnPc and ZnO electronic states and strategically located within the ZnO conduction band and below the ZnPc LUMO. This level induces appreciable changes in the ZnPc absorption spectrum and is expected to significantly favor a molecule-to-surface transfer of photo-excited electrons, a key process in the functioning of hybrid photovoltaic devices. The molecule–surface interactions are also characterized by significant van der Waals forces and by the formation of molecule–surface chemical bonds, thus resulting in appreciable molecular adhesion to the surface.

Tuning of the optical properties of In-rich InxGa1-xN (x=0.82-0.49) alloys by light-ion irradiation at low energy

Abstract The structure and thermodynamics of some gas phase molecular reactants [As 2 , As 4 , Ga(CH 3 ) 3 ] used in MBE (molecular beam epitaxy) and MO-MBE (metal-organic molecular beam epitaxy) has been studied by Hartree-Fock-Roothaan molecular-orbitals linear-combination-of-atomic-orbitals self-consistent-field (HFR-MO-LCAO-SCF) ab initio methods. A first attempt to simulate the sticking of a gallium atom at the (100) surface of GaAs has also been made.