S. Cottenier

The ABINIT project: Impact, environment and recent developments

X. Gonze, B. Amadon, G. Antonius, F. Arnardi, L. Baguet, J.-M. Beuken, J. Bieder, F. Bottin, J. Bouchet, E. Bousquet, N. Brouwer, F. Bruneval, G. Brunin, T. Cavignac, J.-B. Charraud, W. Chen, M. Côté, S. Cottenier, J. Denier, G. Geneste, P. Ghosez, M. Giantomassi, Y. Gillet, O. Gingras, D.R. Hamann, G. Hautier, X. He, N. Helbig, N.A.W. Holzwarth, Y. Jia, F. Jollet, W. Lafargue-Dit-Hauret, K. Lejaeghere, M.A.L. Marques, A. Martin, C. Martins, H.P.C. Miranda, F. Naccarato, K. Persson, G. Petretto, V. Planes, Y. Pouillon, S. Prokhorenko, F. Ricci, G.-M. Rignanese, A.H. Romero, M.M. Schmitt, M. Torrent, M.J. van Setten, B. Van Troeye, M.J. Verstraete, G. Zérah, J.W. Zwanziger
Computer Physics Communications
248, 107042
2020
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Abstract 

Abinit is a material- and nanostructure-oriented package that implements density-functional theory (DFT) and many-body perturbation theory (MBPT) to find, from first principles, numerous properties including total energy, electronic structure, vibrational and thermodynamic properties, different dielectric and non-linear optical properties, and related spectra. In the special issue to celebrate the 40th anniversary of CPC, published in 2009, a detailed account of Abinit was included [Gonze et al. (2009)], and has been amply cited. The present article comes as a follow-up to this 2009 publication. It includes an analysis of the impact that Abinit has had, through for example the bibliometric indicators of the 2009 publication. Links with several other computational materials science projects are described. This article also covers the new capabilities of Abinit that have been implemented during the last three years, complementing a recent update of the 2009 article published in 2016. Physical and technical developments inside the abinit application are covered, as well as developments provided with the Abinit package, such as the multibinit and a-tdep projects, and related Abinit organization developments such as AbiPy . The new developments are described with relevant references, input variables, tests, and tutorials.

210Po production in the European DEMO fusion reactor

M.A.J. Mertens, U. Fischer, P. Pereslavtsev, R. Stieglitz, J.-M. Noterdaeme, S. Cottenier
Nuclear Fusion
59 (10), 106029
2019
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Abstract 

The radionuclide inventory plays a central role in the safety of nuclear installations both during operation and their decommissioning. In nuclear fusion reactors using Pb-Li tritium breeding blankets, the undesired production of radiotoxic 210Po is still an unresolved safety issue. In this work, neutron transport calculations and inventory calculations are combined to predict the 210Po inventory in a DEMO fusion reactor using either a Helium Cooled Lithium Lead or a Water Cooled Lithium Lead breeding blanket. In order to guarantee that the environmental 210Po release associated with an ex-vessel leak-of-PbLi accident remains below the no-evacuation limit, the 210Po concentration in the Pb-Li should be kept below 1500 appt. It was found that no Pb-Li purification is required to keep the 210Po concentration in DEMO below this limit. However, in case the Pb-Li makes direct contact with water, more volatile Po-containing (oxy-)hydroxides could form. If these species increase the 210Po release rate by more than a factor two, safety measures will be required. Therefore, 210Po generation in DEMO does not pose a hazard in case of a regular ex-vessel leak-of-PbLi accident, unless possibly in case the Pb-Li makes contact with water.

Po-Containing Molecules in Fusion and Fission Reactors

M.A.J. Mertens, A. Aerts, I. Infante, J. Neuhausen, S. Cottenier
Journal of Physical Chemistry Letters
10 (11), 2879-2884
2019
A1

Abstract 

Fission and fusion reactors can only play a role in the future energy landscape if they are inherently safe by design. For some reactor concepts, a major remaining issue is the undesired production of radiotoxic 210Po. To filter out the volatile Po species, information on their molecular composition is needed. An experimental characterization is very challenging due to the large required amount of radioactive Po. An alternative quantum chemistry approach was taken to predict the temperature-dependent stability of relevant diatomic Po-containing molecules. Experimental data on lighter analogue molecules was used to establish a well-founded methodology. The relative occurrence of the Po species was estimated in the cover gas of (i) the lead–bismuth eutectic coolant in the accelerator-driven MYRRHA fission reactor and (ii) the Pb–Li eutectic tritium breeder in the DEMO fusion reactor. In both systems, Po is found to occur mainly as PbPo molecules and atomic Po.

Density functional theory study on the B doping and B/P codoping of Si nanocrystals embedded in SiO2

Z.Y. Ni, X.D. Pi, S. Cottenier, D.R. Yang
Physical Review B
95 (7), 075307
2017
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Abstract 

Doping silicon nanocrystals (Si NCs) embedded in silicon dioxide (SiO2) with boron (B) and phosphorus (P) is a promising way of tuning the properties of Si NCs. Here we take advantage of density functional theory to investigate the dependence of the structural and electronic properties of Si NCs embedded in SiO2 on the doping of B and P. The locations and energy-level schemes are examined for singularly B-doped or B/P-codoped Si NCs embedded in SiO2 with a perfect or defective Si/SiO2 interface at which a Si dangling bond exists. A dangling bond plays an important role in the doping of Si NCs with B or B/P. The doping behavior of B in Si NCs embedded in SiO2 vastly differs from that of P. The electronic structure of a B/P-codoped Si NC largely depends on the distribution of the dopants in the NC.

Green Open Access

Formation, Structures and Electronic Properties of Silicene Oxides on Ag(111)

M. Ali, Z.Y. Ni, S. Cottenier, Y. Liu, X.D. Pi, D.R. Yang
Journal of Materials Science & Technology
33 (7), 751-757
2017
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Abstract 

The formation, structural and electronic properties of silicene oxides (SOs) that result from the oxidation of silicene on Ag(111) surface have been investigated in the framework of density functional theory (DFT). It is found that the honeycomb lattice of silicene on the Ag(111) surface changes after the oxidation. SOs are strongly hybridized with the Ag(111) surface so that they possess metallic band structures. Charge accumulation between SOs and the Ag(111) surface indicates strong chemical bonding, which dramatically affects the electronic properties of SOs. When SOs are peeled off the Ag(111) surface, however, they may become semiconductors.

Evaluation of thermodynamics, formation energetics and electronic properties of vacancy defects in CaZrO3

S.M. Alay-e-Abbas, S. Nazir, S. Cottenier, A. Shaukat
Scientific Reports
7, 8439
2017
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Abstract 

Using first-principles total energy calculations we have evaluated the thermodynamics and the electronic properties of intrinsic vacancy defects in orthorhombic CaZrO3. Charge density calculations and the atoms-in-molecules concept are used to elucidate the changes in electronic properties of CaZrO3 upon the introduction of vacancy defects. We explore the chemical stability and defect formation energies of charge-neutral as well as of charged intrinsic vacancies under various synthesis conditions and also present full and partial Schottky reaction energies. The calculated electronic properties indicate that hole-doped state can be achieved in charge neutral Ca vacancy containing CaZrO3 under oxidation condition, while reduction condition allows to control the electrical conductivity of CaZrO3 depending on the charge state and concentration of oxygen vacancies. The clustering of neutral oxygen vacancies in CaZrO3 is examined as well. This provides useful information for tailoring the electronic properties of this material. We show that intentional incorporation of various forms of intrinsic vacancy defects in CaZrO3 allows to considerably modify its electronic properties, making this material suitable for a wide range of applications.

Open Access version available at UGent repository
Green Open Access

Multi-method identification and characterization of the intermetallic surface layers of hot-dip Al-coated steel: FeAl3 or Fe4Al13 and Fe2Al5 or Fe2Al5+x

A. Van Alboom, B. Lemmens, B. Breitbach, E. De Grave, S. Cottenier, K. Verbeken
Surface & Coating Technologies
324, 419-428
2017
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Abstract 

Until now, several different chemical formulae are used to refer to the intermetallic theta-and eta-layers formed at the surface of hot-dip aluminized steel. To clear up the subsequent confusion, both layers were identified and characterized using several experimental techniques combined with DFT calculations.(1) EDX- and EBSD-mappings were performed on the cross section of a hot-dip aluminized steel and showed the presence of the two single phased intermetallic layers, theta and eta, just beneath the aluminum top-layer. The XRD-pattern of a sample of which the top aluminum layer was removed, confirmed the foregoing observations. The compositions of both layers were determined by APT and yield Fe4Al13 and Fe2Al5.6. DFT calculations showed the stability of the Fe4Al13 phase and predicted Fe4Al13 to be the only stable composition in that area of the Fe-Al phase diagram. Based on the DFT results, the ILEEMS spectrum of the theta-layer could be successfully analyzed and, for the first time, fully interpreted in accordance with the crystallographic structure of Fe4Al13. Fe4Al13 is suggested for referring to the composition of the theta-layer, instead of other formulae, e.g. FeAl3. The ILEEMSThlayer spectrum was best reproduced by a model-independent quadrupole splitting distribution, which supports the dis-ordered structure model for the eta-layer. An analysis based on the results of the DFT calculations, confirmed this finding. Because of the partially dis-ordered structure of the eta-layer and the width of the related region in Fe-Al phase diagrams, Fe2Al5-x is suggested for referring to the composition of the eta-layer.

Precipitation in simultaneously nitrided and aged Mo-containing maraging steel

A. Verdiere, C. Hofer, S. De Waele, V. Bliznuk, S. Primig, S. Cottenier, M. D. Tran, B. Pennings, L. A. I. Kestens, R. H. Petrov
Materials Characterization
131, 21-30
2017
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Abstract 

The excellent mechanical properties of maraging steels are ascribed to nanometer-sized intermetallics which precipitate during aging in the ductile very low carbon Ni-martensite. Their wear and fatigue properties can be improved by nitriding. The non-equilibrium precipitation reactions in Fe-Ni-Co-Mo maraging steels are studied during an aging heat treatment executed in a nitriding atmosphere. The precipitates formed during the initial stages of precipitation are characterized with transmission electron microscopy and atom probe tomography. Spherical intermetallic precipitates having a diameter of around 3 nm were detected in the aged, bulk material. These ω-type precipitates formed during the early stages of aging, have a trigonal crystal lattice and their chemical composition is close to (Fe,Ni)7Mo2. In the nitrided layer, Mo-N disc-shaped nitrides on the {100} martensitic lattice having a diameter of 3 to 4 nm were found but their exact crystal structure could not be determined with microstructural characterization techniques. Density functional theory calculations confirmed that a single layer of Mo atoms, substituting Fe on the {100} plane of the Fe-matrix, is stable and showed that the N atoms prefer to be in the Mo-layer, on the octahedral sites with Fe as nearest neighbors.

Adsorption of volatile polonium and bismuth species on metals in various gas atmospheres: Part I - Adsorption of volatile polonium and bismuth on gold

E. A. Maugeri, J. Neuhausen, R. Eichler, R. Dressler, K. Rijpstra, S. Cottenier, D. Piguet, A. Vogele, D. Schumann, A. Bronselaer
RADIOCHIMICA ACTA
104 (11), 757-767
2017
A1

Abstract 

Polonium isotopes are considered the most hazardous radionuclides produced during the operation of accelerator driven systems (ADS) when lead-bismuth eutectic (LBE) is used as the reactor coolant and as the spallation target material. In this work the use of gold surfaces for capturing polonium from the cover gas of the ADS reactor was studied by thermochromatography. The results show that gaseous monoatomic polonium, formed in dry hydrogen, is adsorbed on gold at 1058 K. Its adsorption enthalpy was calculated as -250 +/- 7 kJ mol(-1), using a Monte Carlo simulation code. Highly volatile polonium species that were observed in similar experiments in fused silica columns in the presence of moisture in both inert and reducing gas were not detected in the experiments studying adsorption on gold surfaces. PoO2 is formed in both dry and moist oxygen, and its interaction with gold is characterized by transport reactions. The interaction of bismuth, present in large amounts in the atmosphere of the ADS, with gold was also evaluated. It was found that bismuth has a higher affinity for gold, compared to polonium, in an inert, reducing, and oxidizing atmosphere. This fact must be considered when using gold as a material for filtering polonium in the cover gas of ADS.

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