18 research outputs found
Electronic structure and phase stability of oxide semiconductors: Performance of dielectric-dependent hybrid functional DFT, benchmarked against band structure calculations and experiments
We investigate band gaps, equilibrium structures, and phase stabilities of
several bulk polymorphs of wide-gap oxide semiconductors ZnO, TiO2,ZrO2, and
WO3. We are particularly concerned with assessing the performance of hybrid
functionals built with the fraction of Hartree-Fock exact exchange obtained
from the computed electronic dielectric constant of the material. We provide
comparison with more standard density-functional theory and GW methods. We
finally analyze the chemical reduction of TiO2 into Ti2O3, involving a change
in oxide stoichiometry. We show that the dielectric-dependent hybrid functional
is generally good at reproducing both ground-state (lattice constants, phase
stability sequences, and reaction energies) and excited-state (photoemission
gaps) properties within a single, fully ab initio framework.Comment: Minor changes in the final published versio
Defect calculations in semiconductors through a dielectric-dependent hybrid DFT functional: the case of oxygen vacancies in metal oxides
We investigate the behavior of oxygen vacancies in three different
metal-oxide semiconductors (rutile and anatase TiO2, monoclinic WO3, and
tetragonal ZrO2) using a recently proposed hybrid density-functional method in
which the fraction of exact exchange is material-dependent but obtained ab
initio in a self-consistent scheme. In particular, we calculate
charge-transition levels relative to the oxygen-vacancy defect and compare
computed optical and thermal excitation/emission energies with the available
experimental results, shedding light on the underlying excitation mechanisms
and related materials properties. We find that this novel approach is able to
reproduce not only ground-state properties and band structures of perfect bulk
oxide materials, but also provides results consistent with the optical and
electrical behavior observed in the corresponding substoichiometric defective
systems.Comment: Accepted for publication in J. Chem. Phy
Oxidation of carbynes: signatures in infrared spectra
We report and solidly interpret the infrared spectrum of both pristine and oxidized carbynes embedded in a pure-carbon matrix. The spectra probe separately the effects of oxidation on sp- and on sp 2-hybridized carbon, and provide information on the stability of the different structures in an oxidizing atmosphere. The final products are mostly short end-oxidized carbynes anchored with a double bond to sp 2 fragments, plus an oxidized sp 2 amorphous matrix. Our results have important implications for the realization of carbyne-based nano-electronics devices and highlight the active participation of carbynes in astrochemical reactions where they act as carbon source for the promotion of more complex organic species
Spectroscopie théorique de systèmes réalistes en physique de la matière condensée
PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceItalyFRI
Comment on "Charge-Density Wave and Superconducting Dome in TiSe2 from Electron-Phonon Interaction"
International audienc
Middle paleolithic human deciduous incisor from Grotta del Cavallo, Italy
Objectives: In this contribution, we present a morphological description and comparative morphometric
analysis of Cavallo D, a human tooth unearthed from the Mousterian FIII sublayer of Grotta
del Cavallo (Apulia, Italy).
Materials and Methods: We used microCT data to provide a detailed morphological description
and morphometric analysis of the Cavallo D human tooth based on traditional diameter measurements
and 3D enamel thickness. Moreover, new AMS radiocarbon dating of charcoals from layers
FII was carried out.
Results: Morphological features observed in Cavallo D align the tooth to Neandertals. Similarly,
the large size of the tooth (e.g., BL diameter) and the relatively thinner enamel thickness are typical
Neandertal traits. 14C datings of layer FII attribute the tooth to a time range of 45,600–42,900 cal
BP (at 68% level of probability).
Discussion: Up to now, the Rdi1 Cavallo D represents the most recent Neandertal human remain
in southern Italy related to a radiocarbon dated stratigraphy. Moreover, since deciduous teeth
have been less investigated than the permanent ones, this contribution brings new data to
increase our knowledge on the variability of the Neandertal deciduous dentitio