References of "Dewandre, Antoine"
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See detailCounterintuitive Dynamic Charge in Transition Metal Dichalcogenides and structural change of their heterostructures
Dewandre, Antoine ULiege; Pike, Nicholas ULiege; Ratz, Thomas ULiege et al

Conference (2018, March 05)

Despite numerous studies of transition metal dichalcogenides, the diversity of their chemical bonding characteristics and charge transfer is not well understood. Based on density functional theory we ... [more ▼]

Despite numerous studies of transition metal dichalcogenides, the diversity of their chemical bonding characteristics and charge transfer is not well understood. Based on density functional theory we investigate their static and dynamic charges. The dynamic charge of the transition metal dichalcogenides with trigonal symmetry are anomalously large, while in their hexagonally symmetric counterparts, we even observe a counterintuitive sign, i.e., the transition metal takes a negative charge, opposite to its static charge. This phenomenon, so far never analyzed, is understood by investigating the perturbative response of the system and by investigating the hybridization of the molecular orbitals near the Fermi level. Employing a high-throughput search we also identify other materials that present counterintuitive dynamic charges. Finally, heterostructures of symmetry-equivalent Dichalcogenides are investigated. [less ▲]

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See detailVibrational and dielectric properties of the bulk transition metal dichalcogenides
Pike, Nicholas ULiege; Dewandre, Antoine ULiege; Van Troeye, B. et al

in Physical Review Materials (2018)

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See detailOrigin of the counterintuitive dynamic charge in the transition metal dichalcogenides
Pike, Nicholas ULiege; Van Troeye, Benoit; Dewandre, Antoine ULiege et al

in Physical Review. B (2017), 95

Despite numerous studies of transition metal dichalcogenides, the diversity of their chemical bonding characteristics and charge transfer is not well understood. Based on density functional theory we ... [more ▼]

Despite numerous studies of transition metal dichalcogenides, the diversity of their chemical bonding characteristics and charge transfer is not well understood. Based on density functional theory we investigate their static and dynamic charges. The dynamic charge of the transition metal dichalcogenides with trigonal symmetry are anomalously large, while in their hexagonally symmetric counterparts, we even observe a counterintuitive sign, i.e., the transition metal takes a negative charge, opposite to its static charge. This phenomenon, so far never remarked on or analyzed, is understood by investigating the perturbative response of the system and by investigating the hybridization of the molecular orbitals near the Fermi level. Furthermore, a link is established between the sign of the Born effective charge and the process of π backbonding from organic chemistry. Experiments are proposed to verify the calculated sign of the dynamical charge in these materials. Employing a high-throughput search we also identify other materials that present counterintuitive dynamic charges. [less ▲]

Detailed reference viewed: 91 (14 ULiège)
See detailOrigin of the Counterintuitive Dynamic Charge in the Transition Metal Dichalcogenides
Pike, Nicholas ULiege; Dewandre, Antoine ULiege; Van Troeye, Benoit et al

Scientific conference (2017, March)

Our recent first-principles calculations of the electronic and vibrational properties of the hexagonal transition-metal dichalcogenides reveal that their Born effective charges display a counterintuitive ... [more ▼]

Our recent first-principles calculations of the electronic and vibrational properties of the hexagonal transition-metal dichalcogenides reveal that their Born effective charges display a counterintuitive sign when compared to most other materials or transition-metal dichalcogenides with trigonal symmetry. We determine the origin of this counterintuitive sign by calculating the electronic, vibrational, and optical properties of these systems. We show that the sign of the Born effective charge is directly related to the electric field response of the electronic density, and, in turn, to the bonding characteristics of the material.There is a filled anti-bonding molecular orbital at the Fermi level, which is localized on the transition-metal atom and corresponds to a form of solid state $\pi$ back-bonding in these material. We propose a method of determining if other materials display a similar counterintuitive sign, based on their bonding characteristics, and propose experiments which could measure the sign of the Born effective charge using different spectroscopies. [less ▲]

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See detailCoupled Boltzmann Equation Solver: Effects of the Electron-Phonon Interaction on the Transport Coefficients
Pike, Nicholas ULiege; Dewandre, Antoine ULiege; Verstraete, Matthieu ULiege

Scientific conference (2016, September 22)

Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann ... [more ▼]

Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann equations for the electron and phonon baths within the relaxation time approximation which we use to calculate the thermoelectric transport coefficients. Our model for the coupled Boltzmann Equation solver includes analytic models, including ${\bf k \cdot p}$ Hamiltonians and tight-binding Hamiltonians, for both the electron and phonon energies and analytic models for the electron and phonon relaxation mechanisms. From these calculations we hope to better understand the role and interplay of electron-phonon and phonon-phonon interactions on the thermoelectric transport coefficients. [1] - Phys. Rev. Lett. ${\bf 114}$, 115901 (2015). [2] - PNAS ${\bf 112}$, 14777-14782 (2015). [less ▲]

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See detailVibrations in the Flat Land- A Study of the Vibrational Properties of the Transition-Metal Dichalcogenides
Pike, Nicholas ULiege; Dewandre, Antoine ULiege; Verstraete, Matthieu ULiege et al

Scientific conference (2016, September 03)

Calculations of the vibrational properties of the transition-metal dichalcoginides depend critically on the lattice parameters, symmetries of the underlying system, and the non-local dispersive ... [more ▼]

Calculations of the vibrational properties of the transition-metal dichalcoginides depend critically on the lattice parameters, symmetries of the underlying system, and the non-local dispersive interaction. Here we present phonon band structure calculations, dielectric tensors, elastic tensors, and Born Effective Charges for the transition-metal dichalcogenides $MoS_2$, $MoSe_2$, $MoTe_2$, $WS_2$, $WSe_2$, $NbS_2$, and $NbSe_2$. We systematically investigate the role of the long-range $e^⁻$-$e^⁻$ interaction, spin-orbit coupling, and pseudo-potential approximation, and highlight their importance on the TMD structural and vibrational properties. We find that the phonon spectrum, calculated with the help of a Grimme's D3 non-local Van der Waals interaction depends strongly on the accuracy of the lattice parameters and slightly on the addition of the non-local Van der Waals interaction in the phonon frequency itself. We also find that the sign of the Born Effective Charges on each atom in the Hexagonal TMDs are the opposite of similarly structured compounds. We explore reasons as to why this occurs. Additionally, our calculation of the dielectric tensor and elastic tensor allow us to describe the mechanical properties of the system which are necessary to know for future device applications. [less ▲]

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See detailBoltzmann Transport Calculations in Systems with Electron-phonon Coupling
Pike, Nicholas ULiege; Dewandre, Antoine ULiege; Di Gennaro, Marco ULiege et al

Scientific conference (2016, June 07)

Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann ... [more ▼]

Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann equations for the electron and phonon baths within the relaxation time approximation to describe the changes in the electron and phonon distributions and thus calculate the thermoelectric transport coefficients. Our model for the coupled system will include tight-binding and ${\bf k \cdot p}$ Hamiltonians for both the electron and phonon energies and analytic calculations for the electron and phonon relaxation mechanisms. From these calculations we hope to better understand the role and interplay of electron-phonon and phonon-phonon interactions on the thermoelectric transport coefficients. [1] - Phys. Rev. Lett. ${\bf 114}$, 115901 (2015). [2] - PNAS ${\bf 112}$, 14777-14782 (2015). [less ▲]

Detailed reference viewed: 231 (9 ULiège)
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See detailTwo-step phase transition in SnSe and the origins of its high power factor from first principles
Dewandre, Antoine ULiege; Hellman, Olle; Bhattacharya, Sandip et al

in Physical Review Letters (2016), 117

Detailed reference viewed: 104 (5 ULiège)
See detailAb-initio Study of Ferecrystals
Dewandre, Antoine ULiege; Verstraete, Matthieu ULiege

Poster (2014, September)

Ferecrystals are a new family of compounds first synthesized in 2007 by the group of D. Johnson at the University of Oregon. These materials consist of inter-growths of dichalcogenide and chalcogenide ... [more ▼]

Ferecrystals are a new family of compounds first synthesized in 2007 by the group of D. Johnson at the University of Oregon. These materials consist of inter-growths of dichalcogenide and chalcogenide layers, and can be written as [(M X)_{1+δ} ]_m [T X_2 ]_n where M = Sn, Pb, Sb, Ni and some rare earths; T = Ti, V, Cr, Nb and Ta; X= S and Se. The integers m and n denote the numbers of consecutive formula unit layers in the different components of the inter-growth. The δ parameter reflects the difference of the in-plane cell constants between components of the inter-growth. This family of nanostructured materials shows promising properties for thermoelectric devices. The compounds studied here are [(SnSe)_1.29 ]_{234} [M oSe_2 ]_1 . We performed structural characterisation and examined the transfer of charge at the interface between the two materials. We show that there is a depletion of charge at the interface between the two compo- nents of the heterostructures and that structural distortions of the SnSe layers in the supercell are similar to those observed in slab calculations. [less ▲]

Detailed reference viewed: 166 (9 ULiège)