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Vers une connaissance microscopique de la structure de verres de phosphate P2O5
Layla Martin-Samos, Nikita S. Shcheblanov, Luigi Giacomazzi, Nicolas Richard, Nadege Ollier, 2020, popular article

Abstract: Les propriétés d’amplification de la lumière des ions terres rares permettent en les incluant comme dopants dans le cœur des fibres optiques d’obtenir des sources laser et des amplificateurs de lumière compacts. Pour réduire la tendance à l’agrégation des terres rares qui diminuent leurs propriétés amplificatrices, le phosphore est employé comme co-dopant dans ces fibres. Cet article montre comment les méthodes de simulation à l’échelle atomique peuvent aider a' l'optimisation de ce co-dopage en contribuant a' une meilleure comprehension de la structure des verres phosphates [1] et des défauts qui leur sont liés [2]. Au CEA-DAM, ces resultats serviront aussi dans le cadre d'etudes sur le developpement de fibres optiques pour des mesures de dosimetrie radiative.
Found in: osebi
Keywords: glasses, P2O5, point defects, ab-initio
Published: 18.09.2020; Views: 584; Downloads: 0
.pdf Fulltext (314,64 KB)

Characterization of Mg low-index surfaces by first-principles
Miha Gunde, 2017, master's thesis

Abstract: In this work, three surfaces, namely, Mg(0001), Mg(10 ̄1 0) and Mg(11 ̄2 0) are investigated by means of Density Functional Theory and Generalized Gradient Approximation first-principle calculations. The surfaces have been characterized in terms of their interlayer distances, surface energies, Projected Density of States and Surface Core Level Shifts. Contrary to what was found in previous studies based on Density Functional Theory-Local Density Approximation, the use of Generalized Gradient Approximation exchange correlation functional unravels the oscillatory behavior of both interlayer distances and Surface Core Level Shifts of Mg(10 ̄1 0). Moreover, the Projected Density Of States of un-reconstructed Mg(11 ̄2 0) exhibit the typical quantisation of electronic levels associated to a 2D-confinement of a 3D nearly-free electron gas, as observed in nano-wires, and a Peierls instability along the unconfined direction. Different possible reconstructions on Mg(11 ̄2 0) have then been investigated. In particular, it is found that the surface energy of (2X1) and (3X1) reconstructions is almost degenerate and lower than the surface energy of the unreconstructed Mg(11 ̄2 0) surface. Because of the quasi-degeneracy of surface energies, Mg(11 ̄2 0) surface should be composed by a combination of all the quasi degenerate phases.
Found in: osebi
Keywords: Density Functional Theory, first-principle calculations, Mg surface, Surface Core-Level Shift, surface relaxation, surface reconstruction
Published: 04.07.2017; Views: 3588; Downloads: 1997
.pdf Fulltext (1,77 MB)

Evidence of enhanced photocurrent response in corannulene films
Nadya Patukhova, Layla Martin Samos, Egona Pavlica, Gvido Bratina, 2017, original scientific article

Abstract: Photoconductivity spectra measured in non-crystalline corannulene thin layers are compared to optical absorption in solution phase and thin films. The unexpected enhanced photoconductivity is correlated with GW–BSE theoretical predictions of corannulene gas-phase excitonic spectra. Theoretical analysis reveals a consistent contribution involving transitions to Super Atomic Molecular Orbitals (SAMOs), a unique set of diffuse orbitals typical of curved conjugated constructs. Results suggest SAMO population via direct photoexcitation as a potential mechanism towards exploiting these diffuse orbitals as conducting channels in suitably assembled quantum nanostructures or solids.
Found in: osebi
Keywords: Coranulene, photoconductivity, thin layers, photoexcitation
Published: 26.09.2017; Views: 1943; Downloads: 125
.pdf Fulltext (644,91 KB)

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