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Richard P, Castellano A, Béjaud R, Baguet L, Bouchet J, Geneste G, Bottin F. Ab Initio Phase Diagram of Gold in Extreme Conditions. Phys Rev Lett 2023; 131:206101. [PMID: 38039479 DOI: 10.1103/physrevlett.131.206101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 08/03/2023] [Accepted: 10/12/2023] [Indexed: 12/03/2023]
Abstract
A phase diagram of gold is proposed in the [0; 1000] GPa and [0; 10 000] K ranges of pressure and temperature, respectively, topologically modified with respect to previous predictions. Using finite-temperature ab initio simulations and nonequilibirum thermodynamic integration, both accelerated by machine learning, we evaluate the Gibbs free energies of three solid phases previously proposed. At room temperature, the face-centered cubic (fcc) phase is stable up to ∼500 GPa whereas the body-centered cubic (bcc) phase only appears above 1 TPa. At higher temperature, we do not highlight any fcc-bcc transition line between 200 and 400 GPa, in agreement with ramp-compressed experiments. The present results only disclose a bcc domain around 140-235 GPa and 6000-8000 K, consistent with the triple point recently found in shock experiments. We demonstrate that this re-stabilization of the bcc phase at high temperature is due to anharmonic effects.
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Affiliation(s)
- P Richard
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoires des Matériaux en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
| | - A Castellano
- NanoMat/Q-Mat/CESAM and European Theoretical Spectroscopy Facility, Université de Liège (B5), B-4000 Liège, Belgium
| | - R Béjaud
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoires des Matériaux en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
| | - L Baguet
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoires des Matériaux en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
| | - J Bouchet
- CEA, DES, IRESNE, DEC F-13108 Saint-Paul-Lez-Durance, France
| | - G Geneste
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoires des Matériaux en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
| | - F Bottin
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoires des Matériaux en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
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Charraud JB, Geneste G, Torrent M, Maillet JB. Machine learning accelerated random structure searching: Application to yttrium superhydrides. J Chem Phys 2022; 156:204102. [DOI: 10.1063/5.0085173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The search for new superhydrides, promising materials for both hydrogen storage and high temperature superconductivity, made great progress, thanks to atomistic simulations and Crystal Structure Prediction (CSP) algorithms. When they are combined with Density Functional Theory (DFT), these methods are highly reliable and often match a great part of the experimental results. However, systems of increasing complexity (number of atoms and chemical species) become rapidly challenging as the number of minima to explore grows exponentially with the number of degrees of freedom in the simulation cell. An efficient sampling strategy preserving a sustainable computational cost then remains to be found. We propose such a strategy based on an active-learning process where machine learning potentials and DFT simulations are jointly used, opening the way to the discovery of complex structures. As a proof of concept, this method is applied to the exploration of tin crystal structures under various pressures. We showed that the α phase, not included in the learning process, is correctly retrieved, despite its singular nature of bonding. Moreover, all the expected phases are correctly predicted under pressure (20 and 100 GPa), suggesting the high transferability of our approach. The method has then been applied to the search of yttrium superhydrides (YH x) crystal structures under pressure. The YH6 structure of space group Im-3m is successfully retrieved. However, the exploration of more complex systems leads to the appearance of a large number of structures. The selection of the relevant ones to be included in the active learning process is performed through the analysis of atomic environments and the clustering algorithm. Finally, a metric involving a distance based on x-ray spectra is introduced, which guides the structural search toward experimentally relevant structures. The global process (active-learning and new selection methods) is finally considered to explore more complex and unknown YH x phases, unreachable by former CSP algorithms. New complex phases are found, demonstrating the ability of our approach to push back the exponential wall of complexity related to CSP.
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Affiliation(s)
| | - G. Geneste
- CEA-DAM, DIF, F-91297 Arpajon Cedex, France
- Université Paris-Saclay, CEA, LMCE, 91680, Bruyères-le-Châtel, France
| | - M. Torrent
- CEA-DAM, DIF, F-91297 Arpajon Cedex, France
- Université Paris-Saclay, CEA, LMCE, 91680, Bruyères-le-Châtel, France
| | - J.-B. Maillet
- CEA-DAM, DIF, F-91297 Arpajon Cedex, France
- Université Paris-Saclay, CEA, LMCE, 91680, Bruyères-le-Châtel, France
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Nielsen JC, Kautzner J, Casado-Arroyo R, Burri H, Callens S, Cowie MR, Dickstein K, Drossart I, Geneste G, Erkin Z, Hyafil F, Kraus A, Kutyifa V, Marin E, Schulze C, Slotwiner D, Stein K, Zanero S, Heidbuchel H, Fraser AG. Remote monitoring of cardiac implanted electronic devices: legal requirements and ethical principles - ESC Regulatory Affairs Committee/EHRA joint task force report. Europace 2021; 22:1742-1758. [PMID: 32725140 DOI: 10.1093/europace/euaa168] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/25/2020] [Indexed: 11/13/2022] Open
Abstract
The European Union (EU) General Data Protection Regulation (GDPR) imposes legal responsibilities concerning the collection and processing of personal information from individuals who live in the EU. It has particular implications for the remote monitoring of cardiac implantable electronic devices (CIEDs). This report from a joint Task Force of the European Heart Rhythm Association and the Regulatory Affairs Committee of the European Society of Cardiology (ESC) recommends a common legal interpretation of the GDPR. Manufacturers and hospitals should be designated as joint controllers of the data collected by remote monitoring (depending upon the system architecture) and they should have a mutual contract in place that defines their respective roles; a generic template is proposed. Alternatively, they may be two independent controllers. Self-employed cardiologists also are data controllers. Third-party providers of monitoring platforms may act as data processors. Manufacturers should always collect and process the minimum amount of identifiable data necessary, and wherever feasible have access only to pseudonymized data. Cybersecurity vulnerabilities have been reported concerning the security of transmission of data between a patient's device and the transceiver, so manufacturers should use secure communication protocols. Patients need to be informed how their remotely monitored data will be handled and used, and their informed consent should be sought before their device is implanted. Review of consent forms in current use revealed great variability in length and content, and sometimes very technical language; therefore, a standard information sheet and generic consent form are proposed. Cardiologists who care for patients with CIEDs that are remotely monitored should be aware of these issues.
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Affiliation(s)
- Jens Cosedis Nielsen
- Department of Cardiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, DK-8200 Aarhus N, Denmark
| | - Josef Kautzner
- Institute for Clinical and Experimental Medicine, Prague and Palacky University Medical School, Olomouc, Czech Republic
| | - Ruben Casado-Arroyo
- Department of Cardiology, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Haran Burri
- Cardiac Pacing Unit, Cardiology Service, University Hospital of Geneva, Geneva, Switzerland
| | - Stefaan Callens
- Centre for Biomedical Ethics and Law, KU Leuven, Leuven, Belgium
| | - Martin R Cowie
- Imperial College London (Royal Brompton Hospital) & National Heart and Lung Institute, Dovehouse Street, London SW3 6LY, UK
| | - Kenneth Dickstein
- University of Bergen, Stavanger University Hospital, Stavanger, Norway
| | | | - Ginger Geneste
- Cyber Security Group, Delft University of Technology, Delft, The Netherlands
| | - Zekeriya Erkin
- Cyber Security Group, Delft University of Technology, Delft, The Netherlands
| | - Fabien Hyafil
- Départment Médico-Universitaire DREAM, Bichat University Hospital, APHP.7, Inserm 1148, Université de Paris, Paris, France
| | | | - Valentina Kutyifa
- University of Rochester Medical Center, Clinical Cardiovascular Research Center, Rochester, NY, USA
| | - Eduard Marin
- School of Computer Science, University of Birmingham, Birmingham, UK.,Telefonica Research, Spain
| | - Christian Schulze
- Division of Cardiology, Angiology, Pneumonology and Intensive Medical Care, Department of Internal Medicine I, University Hospital Jena, Friedrich-Schiller-University Jena, Am Klinikum 1, Jena, Germany
| | - David Slotwiner
- Division of Cardiology, New York Presbyterian Queens and School of Health Policy and Research, Weill Cornell Medical College, New York, NY, USA
| | | | - Stefano Zanero
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Hein Heidbuchel
- Department of Cardiology, UniversityHospital Antwerp, University of Antwerp, Antwerp, Belgium
| | - Alan G Fraser
- School of Medicine, Cardiff University, Cardiff, UK.,Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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Laniel D, Geneste G, Weck G, Mezouar M, Loubeyre P. Hexagonal Layered Polymeric Nitrogen Phase Synthesized near 250 GPa. Phys Rev Lett 2019; 122:066001. [PMID: 30822079 DOI: 10.1103/physrevlett.122.066001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 12/14/2018] [Indexed: 06/09/2023]
Abstract
The nitrogen triple bond dissociates in the 100 GPa pressure range and a rich variety of single-bonded polymeric nitrogen structures unique to this element have been predicted up to the terapascal pressure range. The nonmolecular cubic-gauche (cg-N) structure was first observed above 110 GPa, coupled to high temperature (>2000 K) to overcome the kinetic barrier. A mixture of cg-N with a layered phase was afterwards reported between 120 and 180 GPa. Here, by laser heating pure nitrogen from 180 GPa, a sole crystalline phase is characterized above 240 GPa while an amorphous transparent phase is obtained at pressures below. X-ray diffraction and Raman vibrational data reveal a tetragonal lattice (P4_{2}bc) that matches the predicted hexagonal layered polymeric nitrogen (HLP-N) structure. Density-functional theory calculations which include the thermal and dispersive interaction contributions are performed to discuss the stability of the HLP-N structure.
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Affiliation(s)
- D Laniel
- CEA, DAM, DIF, F-91297 Arpajon, France
- CNES Launcher Directorate, 52 rue J. Hillairet, 75612 Paris CEDEX, France
| | - G Geneste
- CEA, DAM, DIF, F-91297 Arpajon, France
| | - G Weck
- CEA, DAM, DIF, F-91297 Arpajon, France
| | - M Mezouar
- European Synchrotron Radiation Facility, 6 Rue Jules Horowitz BP220, F-38043 Grenoble CEDEX, France
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Pépin CM, Geneste G, Dewaele A, Mezouar M, Loubeyre P. Synthesis of FeH5: A layered structure with atomic hydrogen slabs. Science 2017; 357:382-385. [DOI: 10.1126/science.aan0961] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 06/22/2017] [Indexed: 11/02/2022]
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Trincat S, Edgard-Rosa G, Geneste G, Marnay T. Two-level lumbar total disc replacement: functional outcomes and segmental motion after 4 years. Orthop Traumatol Surg Res 2015; 101:17-21. [PMID: 25579824 DOI: 10.1016/j.otsr.2014.10.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 10/08/2014] [Accepted: 10/17/2014] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Lumbar total disc replacement is an effective treatment for single-level discogenic lower back pain. But the replacement of two disc levels is controversial. HYPOTHESIS Two-level total disc replacement will improve function while preserving spinal motion. MATERIAL AND METHODS A continuous series of 108 patients (51 women, 57 men) surgically treated over two levels with the ProDisc-L implant (Synthes Spine) was evaluated retrospectively with an average follow-up of 4 years. Ninety-three of these patients were operated for L4/L5 and L5/S1 degenerative disc disease, while 15 were operated for L3/L4 and L4/L5 disease. The procedure was carried out through the left retroperitoneal approach in 65 patients, the right retroperitoneal approach in 42 patients and both approaches in 1 patient. The Oswestry score, lumbar VAS and radicular VAS were used to evaluate function. The motion of the prosthetic disc segments was evaluated using Cobb's method. Data were collected prospectively in the context of regular patient monitoring. A retrospective analysis was carried out by an independent examiner. RESULTS The procedure led to a statistically significant improvement in the functional scores. The motion of the upper disc segment was 9° (0°-19°) in flexion/extension and 5.5° (2°-12°) in lateral bending. It was 6.2° (0°-14°) and 1.9° (0°-7°) at the lower disc segment. The range of motion was similar in L3/L4 and L4/L5, but was less in L5/S1. Lack of mobility was not correlated with alterations in the functional outcome. The complication rate was 18%. DISCUSSION Two-level lumbar disc replacement improves spinal function while preserving its mobility. But this procedure is fraught with risks and must be carried out by a highly-experienced team. A longer follow-up is needed to evaluate the sustainability of the results and to detect any adjacent segment disease. The French National Authority for Health (HAS) has recommended against two-level lumbar disc replacement, so it no longer can be performed in France.
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Affiliation(s)
- S Trincat
- Hôpital privé « les Franciscaines », 3, rue Jean-Bouin, 30032 Nîmes, France; 65, avenue Jean-Jaurès, 30900 Nîmes, France.
| | - G Edgard-Rosa
- Clinique du Parc, 50, rue Emile-Combe, 34170 Castelnau-le-Lez, France
| | - G Geneste
- Clinique du Parc, 50, rue Emile-Combe, 34170 Castelnau-le-Lez, France
| | - T Marnay
- Clinique du Parc, 50, rue Emile-Combe, 34170 Castelnau-le-Lez, France
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Sevenet N, Gourdon S, Lafon D, Dupiot-Chiron J, Geneste G, Jones N, Bonnet F, Longy M. Abstract P4-04-04: Targeted resequencing of germline PTEN-negative patients with Cowden disease reveals alternate mechanism of molecular alteration. Cancer Res 2013. [DOI: 10.1158/0008-5472.sabcs13-p4-04-04] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Introduction
Cowden disease belongs to the PTEN hamartoma tumor syndrome (PHTS) group, defined by germline PTEN heterozygous inactivation. Describing the PTEN germline mutation in Cowden disease patients is of particular importance for their breast cancer and thyroid carcinoma predisposition evaluation.
Material & methods
Targeted resequencing was done on germline DNA of 22 index cases patients with a Cowden disease clinically well established since they do not demonstrate any PTEN mutation analyzed using our current screening method (EMMA, Enhanced Mismatch Mutation Analysis, similar to high resolution melting). The 565 exons of 34 genes of interest together with the entire genomic locus of PTEN were captured using the SureSelect oligonucleotide library capture (Agilent technologies). The bioinformatics resources Suredesign, Ensembl human genome v70 and a UCSC repeat masker least stringent were used to create the capture design. This gave us 28405 unique 120-mers oligonucleotide probes which were duplicated 1 to 16 times depending on the GC content or the size of the targeted regions (maximum boosting performance criteria). For each gene of interest, an exon of the surrounding gene was also captured in order to define the extent of gross gene rearrangement. Samples were prepared according the manufacturer's recommendations.
Results
Each of the 22 Cowden disease patients demonstrates a mean rate of 70 intronic mutations in the entire genomic locus of PTEN. All of those for which the minor allelic frequency is unknown, were subjected to splicing site bioinformatic prediction. For one patient, the prediction reveals the apparition of a splicing site in a deep intronic mutation of the large intron 1 of PTEN. Furthermore, next generation sequencing (NGS) seems to be more sensitive than our current screening method since for two patients, a germline mosaic exonic heterozygous inactivating mutation of PTEN was detected and confirmed by Sanger sequencing on different biological samples. The level of mosaicism was evaluated by NGS at 3 to 12% depending on the sample and confirmed by pyrosequencing. In addition, some mutations were identified in exons of genes encoding proteins of the PI3Kinase pathway, which could be involved in disease belonging to the PHTS group. With an increasing sensitivity, NGS is a powerful tool to detect low frequency variant. This could used to explain at a molecular level Cowden disease with no initially detectable PTEN mutation. Clinical and biological rationale, bioinformatics workflow and comprehensive results will be presented.
Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-04-04.
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Affiliation(s)
- N Sevenet
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - S Gourdon
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - D Lafon
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - J Dupiot-Chiron
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - G Geneste
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - N Jones
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - F Bonnet
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
| | - M Longy
- INSERM U916 & Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Oncogenetic Lab, Institut Bergonie, Bordeaux, France; Plateforme Genome Transcriptome, Univ. Bordeaux Segalen, Bordeaux, France
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Rault JE, Dionot J, Mathieu C, Feyer V, Schneider CM, Geneste G, Barrett N. Polarization sensitive surface band structure of doped BaTiO3(001). Phys Rev Lett 2013; 111:127602. [PMID: 24093301 DOI: 10.1103/physrevlett.111.127602] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 07/30/2013] [Indexed: 06/02/2023]
Abstract
We present a spatial and wave-vector resolved study of the electronic structure of micron sized ferroelectric domains at the surface of a BaTiO(3)(001) single crystal. The n-type doping of the BaTiO(3) is controlled by in situ vacuum and oxygen annealing, providing experimental evidence of a surface paraelectric-ferroelectric transition below a critical doping level. Real space imaging of photoemission threshold, core level and valence band spectra show contrast due to domain polarization. Reciprocal space imaging of the electronic structure using linearly polarized light provides unambiguous evidence for the presence of both in- and out-of-plane polarization with two- and fourfold symmetry, respectively. The results agree well with first principles calculations.
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Affiliation(s)
- J E Rault
- CEA, DSM/IRAMIS/SPCSI, F-91191 Gif-sur-Yvette Cedex, France
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Daumont C, Ren W, Infante IC, Lisenkov S, Allibe J, Carrétéro C, Fusil S, Jacquet E, Bouvet T, Bouamrane F, Prosandeev S, Geneste G, Dkhil B, Bellaiche L, Barthélémy A, Bibes M. Strain dependence of polarization and piezoelectric response in epitaxial BiFeO3 thin films. J Phys Condens Matter 2012; 24:162202. [PMID: 22467186 DOI: 10.1088/0953-8984/24/16/162202] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Epitaxial strain has recently emerged as a powerful means to engineer the properties of ferroelectric thin films, for instance to enhance the ferroelectric Curie temperature (T(C)) in BaTiO(3). However, in multiferroic BiFeO(3) thin films an unanticipated strain-driven decrease of T(C) was reported and ascribed to the peculiar competition between polar and antiferrodistortive instabilities. Here, we report a systematic characterization of the room-temperature ferroelectric and piezoelectric properties for strain levels ranging between -2.5% and +1%. We find that polarization and the piezoelectric coefficient increase by about 20% and 250%, respectively, in this strain range. These trends are well reproduced by first-principles-based techniques.
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Affiliation(s)
- C Daumont
- Unité Mixte de Physique CNRS/Thales, Palaiseau, France
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Hu Y, Hernandez O, Broux T, Bahout M, Hermet J, Ottochian A, Ritter C, Geneste G, Dezanneau G. Oxygen diffusion mechanism in the mixed ion-electron conductor NdBaCo2O5+x. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm34396g] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Infante IC, Juraszek J, Fusil S, Dupé B, Gemeiner P, Diéguez O, Pailloux F, Jouen S, Jacquet E, Geneste G, Pacaud J, Íñiguez J, Bellaiche L, Barthélémy A, Dkhil B, Bibes M. Multiferroic phase transition near room temperature in BiFeO3 films. Phys Rev Lett 2011; 107:237601. [PMID: 22182123 DOI: 10.1103/physrevlett.107.237601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Indexed: 05/31/2023]
Abstract
In multiferroic BiFeO(3) thin films grown on highly mismatched LaAlO(3) substrates, we reveal the coexistence of two differently distorted polymorphs that leads to striking features in the temperature dependence of the structural and multiferroic properties. Notably, the highly distorted phase quasiconcomitantly presents an abrupt structural change, transforms from a standard to a nonconventional ferroelectric, and transitions from antiferromagnetic to paramagnetic at 360±20 K. These coupled ferroic transitions just above room temperature hold promises of giant piezoelectric, magnetoelectric, and piezomagnetic responses, with potential in many applications fields.
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Affiliation(s)
- I C Infante
- Unité Mixte de Physique CNRS/Thales, Campus de l'Ecole Polytechnique, 1 avenue Fresnel, 91767 Palaiseau, France
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Dupé B, Prosandeev S, Geneste G, Dkhil B, Bellaiche L. BiFeO3 films under tensile epitaxial strain from first principles. Phys Rev Lett 2011; 106:237601. [PMID: 21770543 DOI: 10.1103/physrevlett.106.237601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Indexed: 05/31/2023]
Abstract
Density-functional calculations are performed to predict structural and magnetic properties of (001) BiFeO(3) films under tensile epitaxial strain. These films remain monoclinic (Cc space group) for misfit strains between 0% and ≈8%, with the polarization, tilt axis and magnetization all rotating when varying the strain. At a tensile strain ≈8%, these films undergo a first-order phase transition towards an orthorhombic phase (Ima2 space group). In this novel phase, the polarization and tilt axis lie in the epitaxial plane, while the magnetization is along the out-of-plane direction and the direction of the antiferromagnetic vector is unchanged by the phase transition. An unexpected additional degree of freedom, namely, an antiphase arrangement of Bi atoms, is also found for all tensile strains.
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Affiliation(s)
- B Dupé
- Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS-UMR 8580, Ecole Centrale Paris, Châtenay-Malabry, France
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13
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Infante IC, Lisenkov S, Dupé B, Bibes M, Fusil S, Jacquet E, Geneste G, Petit S, Courtial A, Juraszek J, Bellaiche L, Barthélémy A, Dkhil B. Bridging multiferroic phase transitions by epitaxial strain in BiFeO3. Phys Rev Lett 2010; 105:057601. [PMID: 20867953 DOI: 10.1103/physrevlett.105.057601] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Indexed: 05/05/2023]
Abstract
We report the influence of epitaxial strain on the multiferroic phase transitions of BiFeO3 films. Using advanced characterization techniques and calculations we show that while the magnetic Néel temperature hardly varies, the ferroelectric Curie temperature TC decreases dramatically with strain. This is in contrast with the behavior of standard ferroelectrics where strain enhances the polar cation shifts and thus TC. We argue that this is caused by an interplay of polar and oxygen tilting instabilities and that strain can drive both transitions close together to yield increased magnetoelectric responses.
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Affiliation(s)
- I C Infante
- Unité Mixte de Physique CNRS/Thales, 1 avenue Fresnel, Campus de l'Ecole Polytechnique, 91767 Palaiseau, France
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Louis L, Gemeiner P, Ponomareva I, Bellaiche L, Geneste G, Ma W, Setter N, Dkhil B. Low-symmetry phases in ferroelectric nanowires. Nano Lett 2010; 10:1177-1183. [PMID: 20230042 DOI: 10.1021/nl9034708] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Ferroelectric nanostructures have recently attracted much attention due to the quest of miniaturizing devices and discovering novel phenomena. In particular, studies conducted on two-dimensional and zero-dimensional ferroelectrics have revealed original properties and their dependences on mechanical and electrical boundary conditions. Meanwhile, researches aimed at discovering and understanding properties of one-dimensional ferroelectric nanostructures are scarce. The determination of the structural phase and of the direction of the polarization in one-dimensional ferroelectrics is of technological importance, since, e.g., a low-symmetry phase in which the polarization lies away from a highly symmetric direction typically generates phenomenal dielectric and electromechanical responses. Here, we investigate the phase transition sequence of nanowires made of KNbO(3) and BaTiO(3) perovskites, by combining X-ray diffraction, Raman spectroscopy, and first-principles-based calculations. We provide evidence of a previously unreported ferroelectric ground state of monoclinic symmetry and the tuning of the polarization's direction by varying factors inherent to the nanoscale.
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Affiliation(s)
- L Louis
- Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS-UMR8580, Ecole Centrale Paris, Grande voie des vignes, Châtenay-Malabry, France
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Béa H, Dupé B, Fusil S, Mattana R, Jacquet E, Warot-Fonrose B, Wilhelm F, Rogalev A, Petit S, Cros V, Anane A, Petroff F, Bouzehouane K, Geneste G, Dkhil B, Lisenkov S, Ponomareva I, Bellaiche L, Bibes M, Barthélémy A. Evidence for room-temperature multiferroicity in a compound with a giant axial ratio. Phys Rev Lett 2009; 102:217603. [PMID: 19519136 DOI: 10.1103/physrevlett.102.217603] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Indexed: 05/12/2023]
Abstract
In the search for multiferroic materials magnetic compounds with a strongly elongated unit-cell (large axial ratio c/a) have been scrutinized intensely. However, none was hitherto proven to have a switchable polarization, an essential feature of ferroelectrics. Here, we provide evidence for the epitaxial stabilization of a monoclinic phase of BiFeO3 with a giant axial ratio (c/a=1.23) that is both ferroelectric and magnetic at room temperature. Surprisingly, and in contrast with previous theoretical predictions, the polarization does not increase dramatically with c/a. We discuss our results in terms of the competition between polar and antiferrodistortive instabilities and give perspectives for engineering multiferroic phases.
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Affiliation(s)
- H Béa
- Unité Mixte de Physique CNRS/Thales, Campus de l'Ecole Polytechnique, 1 Av. A. Fresnel, 91767 Palaiseau, France
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Macgrogan G, Hostein I, Chibon F, Geneste G, Petersen M, Velasco V, De Mascarel I, Soubeyran I, Bui M, Coindre J, Parrens M, De Mascarel A, Belaud-Rotureau M, Idrissi Y, Turmot M, Merlio J, Bonnet J, Colotte M, Tuffet S. Accélération de la fixation par le micro-ondes : l’expérience bordelaise. Ann Pathol 2007. [DOI: 10.1016/s0242-6498(07)92881-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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