98 research outputs found
Ionization Potentials of First-Row Transition Metal Aqua Ions
We report computations of the vertical ionization potentials within the
approximation of the near-complete series of first-row transition metal (V-Cu)
aqua ions in their most common oxidation states, i.e. V, Cr,
Cr, Mn, Fe, Fe, Co, Ni, and
Cu. The -orbital occupancy of these systems spans a broad range from
to . All the structures were first optimized at the density
functional theory level using a large cluster of explicit water molecules that
are embedded in a continuum solvation model. Vertical ionization potentials
were computed with the one-shot approach on a range of transition
metal ion clusters (6, 18, 40, and 60 explicit water molecules) wherein the
convergence with respect to the basis set size was evaluated using the systems
with 40 water molecules. We assess the results using three different density
functional approximations as starting points for the vertical ionization
potential calculations, namely @PBE, @PBE0, and
@rSCAN. While the predicted ground-state structures are similar
with all three exchange-correlation functionals, the vertical ionization
potentials were in closer agreement with the experiment when using the
@PBE0 and @rSCAN approaches, with the r2SCAN based
calculations being significantly less expensive. Computed bond distances and
vertical ionization potentials for all structures were compared with available
experimental data and are in good agreement
Interaction of nanodiamonds with water: Impact of surface chemistry on hydrophilicity, aggregation and electrical properties
In recent decades, nanodiamonds (NDs) have earned increasing interest in a wide variety of research fields, thanks to their excellent mechanical, chemical, and optical properties, together with the possibility of easily tuning their surface chemistry for the desired purpose. According to the application context, it is essential to acquire an extensive understanding of their interaction with water in terms of hydrophilicity, environmental adsorption, stability in solution, and impact on electrical properties. In this paper, we report on a systematic study of the effects of reducing and oxidizing thermal processes on ND surface water adsorption. Both detonation and milled NDs were analyzed by combining different techniques. Temperature-dependent infrared spectroscopy was employed to study ND surface chemistry and water adsorption, while dynamic light scattering allowed the evaluation of their behavior in solution. The influence of water adsorption on their electrical properties was also investigated and correlated with structural and optical information obtained via Raman/photoluminescence spectroscopy. In general, higher oxygen-containing surfaces exhibited higher hydrophilicity, better stability in solution, and higher electrical conduction, although for the latter the surface graphitic contribution was also crucial. Our results provide in-depth information on the hydrophilicity of NDs in relation to their surface chemical and physical properties, by also evaluating the impacts on their aggregation and electrical conductance
Fabrication of quantum emitters in aluminium nitride by Al-ion implantation and thermal annealing
Single-photon emitters (SPEs) within wide-bandgap materials represent an
appealing platform for the development of single-photon sources operating at
room temperatures. Group III- nitrides have previously been shown to host
efficient SPEs which are attributed to deep energy levels within the large
bandgap of the material, in a way that is similar to extensively investigated
colour centres in diamond. Anti-bunched emission from defect centres within
gallium nitride (GaN) and aluminium nitride (AlN) have been recently
demonstrated. While such emitters are particularly interesting due to the
compatibility of III-nitrides with cleanroom processes, the nature of such
defects and the optimal conditions for forming them are not fully understood.
Here, we investigate Al implantation on a commercial AlN epilayer through
subsequent steps of thermal annealing and confocal microscopy measurements. We
observe a fluence-dependent increase in the density of the emitters, resulting
in creation of ensembles at the maximum implantation fluence. Annealing at 600
{\deg}C results in the optimal yield in SPEs formation at the maximum fluence,
while a significant reduction in SPE density is observed at lower fluences.
These findings suggest that the mechanism of vacancy formation plays a key role
in the creation of the emitters, and open new perspectives in the defect
engineering of SPEs in solid state.Comment: 11 pages, 7 figure
Efficient fabrication of high-density ensembles of color centers via ion implantation on a hot diamond substrate
Nitrogen-Vacancy (NV) centers in diamond are promising systems for quantum
technologies, including quantum metrology and sensing. A promising strategy for
the achievement of high sensitivity to external fields relies on the
exploitation of large ensembles of NV centers, whose fabrication by ion
implantation is upper limited by the amount of radiation damage introduced in
the diamond lattice. In this works we demonstrate an approach to increase the
density of NV centers upon the high-fluence implantation of MeV N2+ ions on a
hot target substrate (>550 {\deg}C). Our results show that, with respect to
room-temperature implantation, the high-temperature process increases the
vacancy density threshold required for the irreversible conversion of diamond
to a graphitic phase, thus enabling to achieve higher density ensembles.
Furthermore, the formation efficiency of color centers was investigated on
diamond substrates implanted at varying temperatures with MeV N2+ and Mg+ ions
revealing that the formation efficiency of both NV centers and
magnesium-vacancy (MgV) centers increases with the implantation temperature.Comment: 12 pages, 5 figure
Cohesive properties of alkali halides
We calculate cohesive properties of LiF, NaF, KF, LiCl, NaCl, and KCl with
ab-initio quantum chemical methods. The coupled-cluster approach is used to
correct the Hartree-Fock crystal results for correlations and to systematically
improve cohesive energies, lattice constants and bulk moduli. After inclusion
of correlations, we recover 95-98 % of the total cohesive energies. The lattice
constants deviate from experiment by at most 1.1 %, bulk moduli by at most 8 %.
We also find good agreement for spectroscopic properties of the corresponding
diatomic molecules.Comment: LaTeX, 10 pages, 1 figure, accepted by Phys. Rev.
Lucio D'ambra : il cinema
Analisi dell'attività cienmatografica dello sceneggiatore, regista, produttore, nonché critico e teorico cinematografico Lucio d'Ambr
Lucio D'ambra : il cinema
Analisi dell'attività cienmatografica dello sceneggiatore, regista, produttore, nonché critico e teorico cinematografico Lucio d'Ambr
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