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Dubiel SM, Hu MY, Sternik M, Ercan Alp E, Alatas A, Said A, Parlinski K, Piekarz P. Lattice dynamics of 119Sn impurity in a bcc-Cr crystal. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:455402. [PMID: 39111341 DOI: 10.1088/1361-648x/ad6c97] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 08/07/2024] [Indexed: 08/24/2024]
Abstract
The chromium crystal doped with119Sn isotope was studied using the nuclear resonance inelastic x-ray scattering and first principles calculations. The Sn partial phonon density of states (PDOS) was obtained for three temperatures that correspond to different magnetic states of Cr. At all temperatures, the energy spectrum consists of a broad band around 18 meV and a narrow peak at 43 meV. The additional peak around 39 meV is observed only in the magnetically ordered phases, indicating the influence of magnetic order in chromium on lattice dynamics. The partial PDOS calculated with the antiferromagnetic order on Cr atoms show a very good agreement with the experimental data. It is revealed that the high-energy peak is lying above the phonon spectra of the pure bcc-Cr crystal. These are the local modes with the increased energies due to a strongly reduced distance between Sn and the nearest-neighbor Cr atoms.
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Affiliation(s)
- Stanisław M Dubiel
- AGH University of Kraków, Faculty of Physics and Applied Computer Science, Kraków, PL 30-059, Poland
| | - Michael Y Hu
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, United States of America
| | - Małgorzata Sternik
- Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, PL 31-342, Poland
| | - E Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, United States of America
| | - Ahmet Alatas
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, United States of America
| | - Ayman Said
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, United States of America
| | - Krzysztof Parlinski
- Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, PL 31-342, Poland
| | - Przemysław Piekarz
- Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, PL 31-342, Poland
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Onyango I, Collinge G, Wang Y, McEwen JS. Distribution Tendencies of Noble Metals on Fe(100) Using Lattice Gas Cluster Expansions. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:9504-9512. [PMID: 38894752 PMCID: PMC11182028 DOI: 10.1021/acs.jpcc.4c01402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2024] [Revised: 05/04/2024] [Accepted: 05/14/2024] [Indexed: 06/21/2024]
Abstract
Fe-based catalysts are highly selective for the hydrodeoxygenation of biomass-derived oxygenates but are prone to oxidative deactivation. Promotion with a noble metal has been shown to improve oxidative resistance. The chemical properties of such bimetallic systems depend critically on the surface geometry and spatial configuration of surface atoms in addition to their coverage (i.e., noble metal loading), so these aspects must be taken into account in order to develop reliable models for such complex systems. This requires sampling a vast configurational space, which is rather impractical using density functional theory (DFT) calculations alone. Moreover, "DFT-based" models are limited to length scales that are often too small for experimental relevance. Here, we circumvent this challenge by constructing DFT-parametrized lattice gas cluster expansions (LG CEs), which can describe these types of systems at significantly larger length scales. Here, we apply this strategy to Fe(100) promoted with four technologically relevant precious metals: Pd, Pt, Rh, and Ru. The resultant LG CEs have remarkable predictive accuracy, with predictive errors below 10 meV/site over a coverage range of 0 to 2 monolayers. The ground state configurations for each noble metal were identified, and the analysis of the cluster energies reveals a significant disparity in their dispersion tendency.
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Affiliation(s)
- Isaac Onyango
- The
Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States
| | - Greg Collinge
- The
Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States
| | - Yong Wang
- The
Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States
- Institute
for Integrated Catalysis, Pacific Northwest
National Laboratory, Richland, Washington 99354, United States
| | - Jean-Sabin McEwen
- The
Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States
- Institute
for Integrated Catalysis, Pacific Northwest
National Laboratory, Richland, Washington 99354, United States
- Department
of Physics and Astronomy, Washington State
University, Pullman, Washington 99164, United States
- Department
of Chemistry, Washington State University, Pullman, Washington 99164, United States
- Department
of Biological Systems Engineering, Washington
State University, Pullman, Washington 99164, United States
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Belozerov AS, Katanin AA, Anisimov VI. Itinerant magnetism of chromium under pressure: a DFT+DMFT study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:385601. [PMID: 34198275 DOI: 10.1088/1361-648x/ac1090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/01/2021] [Indexed: 06/13/2023]
Abstract
We consider electronic and magnetic properties of chromium, a well-known itinerant antiferromagnet, by a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT). We find that electronic correlation effects in chromium, in contrast to its neighbors in the periodic table, are weak, leading to the quasiparticle mass enhancement factorm*/m≈ 1.2. Our results for local spin-spin correlation functions and distribution of weights of atomic configurations indicate that the local magnetic moments are not formed. Similarly to previous results of DFT at ambient pressure, the non-uniform magnetic susceptibility as a function of momentum possesses close to the wave vectorQH= (0, 0, 2π/a) (ais the lattice constant) sharp maxima, corresponding to Kohn anomalies. We find that these maxima are preserved by the interaction and are not destroyed by pressure. Our calculations qualitatively capture a decrease of the Néel temperature with pressure and a breakdown of itinerant antiferromagnetism at pressure of ∼9 GPa in agreement with experimental data, although the Néel temperature is significantly overestimated because of the mean-field nature of DMFT.
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Affiliation(s)
- A S Belozerov
- M. N. Miheev Institute of Metal Physics, Russian Academy of Sciences, 620108 Yekaterinburg, Russia
| | - A A Katanin
- M. N. Miheev Institute of Metal Physics, Russian Academy of Sciences, 620108 Yekaterinburg, Russia
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
| | - V I Anisimov
- M. N. Miheev Institute of Metal Physics, Russian Academy of Sciences, 620108 Yekaterinburg, Russia
- Ural Federal University, 620002 Yekaterinburg, Russia
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Flat-Band in Pyrochlore Oxides: A First-Principles Study. NANOMATERIALS 2019; 9:nano9060876. [PMID: 31185681 PMCID: PMC6631565 DOI: 10.3390/nano9060876] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 06/06/2019] [Accepted: 06/07/2019] [Indexed: 11/17/2022]
Abstract
Using a first-principles electronic band calculation, we obtained a quasi flat-band near the Fermi level for the six pyrochlore oxides, A2B2O7. These quasi flat-bands are mostly characterized by the s-orbitals of the A-site. The band structures of these oxides are well described by the non-interacting Mielke model. Spin-polarized calculations showed that the ground state of these compounds was ferromagnetic after appropriate carrier doping, despite the absence of the magnetic element.
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Bragato M, Achilli S, Cargnoni F, Ceresoli D, Martinazzo R, Soave R, Trioni MI. Magnetic Moments and Electron Transport through Chromium-Based Antiferromagnetic Nanojunctions. MATERIALS (BASEL, SWITZERLAND) 2018; 11:E2030. [PMID: 30340431 PMCID: PMC6213584 DOI: 10.3390/ma11102030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 09/20/2018] [Accepted: 10/17/2018] [Indexed: 11/16/2022]
Abstract
We report the electronic, magnetic and transport properties of a prototypical antiferromagnetic (AFM) spintronic device. We chose Cr as the active layer because it is the only room-temperature AFM elemental metal. We sandwiched Cr between two non-magnetic metals (Pt or Au) with large spin-orbit coupling. We also inserted a buffer layer of insulating MgO to mimic the structure and finite resistivity of a real device. We found that, while spin-orbit has a negligible effect on the current flowing through the device, the MgO layer plays a crucial role. Its effect is to decouple the Cr magnetic moment from Pt (or Au) and to develop an overall spin magnetization. We have also calculated the spin-polarized ballistic conductance of the device within the Büttiker⁻Landauer framework, and we have found that for small applied bias our Pt/Cr/MgO/Pt device presents a spin polarization of the current amounting to ≃25%.
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Affiliation(s)
- Marco Bragato
- Department of Chemistry, University of Milan, 20133 Milan, Italy.
| | - Simona Achilli
- Department of Physics, University of Milan, 20133 Milan, Italy.
| | - Fausto Cargnoni
- Consiglio Nazionale delle Ricerche, Istituto di Scienze e Tecnologie Molecolari and INSTM UdR di Milano, via Golgi 19, 20133 Milan, Italy.
| | - Davide Ceresoli
- Consiglio Nazionale delle Ricerche, Istituto di Scienze e Tecnologie Molecolari and INSTM UdR di Milano, via Golgi 19, 20133 Milan, Italy.
| | - Rocco Martinazzo
- Department of Chemistry, University of Milan, 20133 Milan, Italy.
| | - Raffaella Soave
- Consiglio Nazionale delle Ricerche, Istituto di Scienze e Tecnologie Molecolari and INSTM UdR di Milano, via Golgi 19, 20133 Milan, Italy.
| | - Mario Italo Trioni
- Consiglio Nazionale delle Ricerche, Istituto di Scienze e Tecnologie Molecolari and INSTM UdR di Milano, via Golgi 19, 20133 Milan, Italy.
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Habibi P, Barreteau C, Smogunov A. Electronic and magnetic structure of the Cr(001) surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:146002. [PMID: 23478357 DOI: 10.1088/0953-8984/25/14/146002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Density functional theory (DFT) calculations are carried out to study the electronic and magnetic structure of the (001) surface of chromium. Our aim is to identify and characterize the most prominent electronic surface states and make the connection with the main experimental results. We show that a low dispersive minority spin surface state at the center of the surface Brillouin zone plays a crucial role. This surface state of Δ1 symmetry at 0.58 eV above the Fermi level exhibits a predominantly dz(2) as well as pz orbital character. Local density of states (LDOS) analysis in the vacuum above the surface shows that the sharp feature originating from this surface state persists far away above the surface because of the slow decay rate of the pz wavefunction. Finally, by artificially lowering the surface magnetic moment [Formula: see text] on the outermost surface layer we find excellent agreement with experiments for [Formula: see text]. In addition, we propose that some extra spin polarized scanning tunneling spectroscopy (SP-STS) experiments should be made at smaller tip-surface distances to reveal additional features originating from the majority spin dz(2) surface state.
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Affiliation(s)
- P Habibi
- CEA, IRAMIS, SPCSI, F-91191 Gif-sur-Yvette Cedex, France
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