1
|
Ghosh PS, Arya A. Evidence of vacancy ordered structures in PuO 2-x and AmO 2-x from first-principles calculations. Phys Chem Chem Phys 2023; 25:14117-14125. [PMID: 37161928 DOI: 10.1039/d3cp00971h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A combination of first-principles calculations and cluster expansion method is used to study ordering of oxygen vacancies in PuO2-x and AmO2-x. Vacancy ordered stable/metastable structures of composition Pu8O15 (PuO1.875), Pu6O11 (PuO1.833), Pu8O14 (PuO1.75) and Am10O19 (AmO1.90), Am8O15 (AmO1.875), Am10O18 (AmO1.80), Am8O13 (AmO1.625) are identified in PuO2-x and AmO2-x, respectively, from cluster expansion calculations. A comparison of formation enthalpies of vacancy ordered and vacancy disordered structures shows that Am8O15 (AmO1.875) and Am8O13 (AmO1.625) are more stable by 52 and 55 meV per atom, respectively, compared to their disordered counterparts. Similarly, vacancy ordered Pu8O15 (PuO1.875) and Pu8O14 (PuO1.75) structures are more stable compared to the disordered structures by 10 and 8 meV per atom, respectively. In contrast, the disordered PuO1.625 structure is more stable compared to the cluster expansion generated structures. The vacancy ordered structures are mechanically stable and their bulk modulus, Young's modulus, shear modulus and Poisson's ratio are reported.
Collapse
Affiliation(s)
- P S Ghosh
- Glass and Advanced Materials Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, India
| | - A Arya
- Glass and Advanced Materials Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, India
| |
Collapse
|
2
|
Lin X, Huang YC, Hu Z, Li L, Zhou J, Zhao Q, Huang H, Sun J, Pao CW, Chang YC, Lin HJ, Chen CT, Dong CL, Wang JQ, Zhang L. 5f Covalency Synergistically Boosting Oxygen Evolution of UCoO 4 Catalyst. J Am Chem Soc 2021; 144:416-423. [PMID: 34878269 PMCID: PMC8759065 DOI: 10.1021/jacs.1c10311] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Electronic structure
modulation among multiple metal sites is key
to the design of efficient catalysts. Most studies have focused on
regulating 3d transition-metal active ions through other d-block metals,
while few have utilized f-block metals. Herein, we report a new class
of catalyst, namely, UCoO4 with alternative CoO6 and 5f-related UO6 octahedra, as a unique example of
a 5f-covalent compound that exhibits enhanced electrocatalytic oxygen
evolution reaction (OER) activity because of the presence of the U
5f–O 2p–Co 3d network. UCoO4 exhibits a low
overpotential of 250 mV at 10 mA cm–2, surpassing
other unitary cobalt-based catalysts ever reported. X-ray absorption
spectroscopy revealed that the Co2+ ion in pristine UCoO4 was converted to high-valence Co3+/4+, while U6+ remained unchanged during the OER, indicating that only
Co was the active site. Density functional theory calculations demonstrated
that the OER activity of Co3+/4+ was synergistically enhanced
by the covalent bonding of U6+-5f in the U 5f–O
2p–Co 3d network. This study opens new avenues for the realization
of electronic structure manipulation via unique 5f involvement.
Collapse
Affiliation(s)
- Xiao Lin
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Yu-Cheng Huang
- Department of Physics, Tamkang University, Tamsui, New Taipei City 25137, Taiwan, R.O.C
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Lili Li
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Jing Zhou
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Qingyun Zhao
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Haoliang Huang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Jian Sun
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chih-Wen Pao
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, R.O.C
| | - Yu-Chung Chang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, R.O.C
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, R.O.C
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, R.O.C
| | - Chung-Li Dong
- Department of Physics, Tamkang University, Tamsui, New Taipei City 25137, Taiwan, R.O.C
| | - Jian-Qiang Wang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Linjuan Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
4
|
Ghosh PS, Arya A. Structural, thermodynamic, electronic and elastic properties of Th 1-xU xO 2 and Th 1-xPu xO 2 mixed oxides. Phys Chem Chem Phys 2020; 22:6406-6417. [PMID: 32149299 DOI: 10.1039/d0cp00220h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structural, thermodynamic, electronic, and elastic properties of Th1-xUxO2 and Th1-xPuxO2 mixed oxides (MOX) have been calculated with Hubbard corrected density functional theory (DFT+U) to account for the strong 5f electron correlations. The ideal solid solution is approximated by special quasi-random structures and the U-ramping method is used to account for the presence of metastable states in the self-consistent field solution of the DFT+U approach. The mixing enthalpy (ΔHmix) is positive throughout the composition range of the Th1-xUxO2 MOX, consistent with a simple miscibility gap (at low temperature) phase diagram. The behavior of the Th1-xPuxO2 MOX is more complex, where ΔHmix is positive in the ThO2-rich region and negative in the PuO2-rich region. Electronic structure analysis shows that substitution of Th by U/Pu in ThO2 leads to a reduction of the average Th-O bond lengths, causing distortion in the crystal structure. The distortion in the crystal structure results in an increase in the conduction bandwidth and a reduction of the band-gap in the MOX. Good agreement of our DFT+U calculated elastic properties of ThO2, UO2 and PuO2 compounds with experiments leads to convincing prediction of these properties for Th1-xUxO2 and Th1-xPuxO2 MOX.
Collapse
Affiliation(s)
- P S Ghosh
- Glass & Advanced Materials Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
| | - A Arya
- Glass & Advanced Materials Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
| |
Collapse
|
5
|
Ghosh PS, Arya A. First-principles study of phase stability, electronic and mechanical properties of plutonium sub-oxides. Phys Chem Chem Phys 2019; 21:16818-16829. [PMID: 31334519 DOI: 10.1039/c9cp01858a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The formation energies (ΔHf) of fluorite PuO2, α-Pu2O3 and sub-oxides PuO2-x (0.0 < x < 0.5) are determined from atomic scale simulations based on density functional theory (DFT) employing the generalised gradient approximation (GGA) corrected with an effective Hubbard parameter (Ueff). The variation of structural and electronic properties of PuO2 and α-Pu2O3 is determined while ramping up Ueff from 0 eV to 5 eV (Ueff-ramping method) to treat the presence of metastable magnetic states and to determine the most suitable Ueff value matching the experiments. The GGA+U calculated lattice parameter variation as a function of stoichiometry (a(x)) for PuO2-x shows a positive volume of relaxation and an almost linear variation presented by the relation a(x) = a0- 0.522738x, where a0 is the equilibrium lattice parameter of PuO2. The GGA+U calculated ΔHf values of PuO2-x lie above the tie line connecting the ΔHf of PuO2 and Pu2O3, and with decreasing O/Pu ratio, the stability of the sub-oxides increases. The crystal and electronic structure analysis of the oxygen vacancy in PuO2 shows outward anisotropic relaxation of four Pu atoms around the vacancy site. The electronic charges within the Wigner-Seitz sphere around these Pu atoms show an overall gain of only (0.12-0.22)e per Pu atom, signifying an incomplete localization of charges. Finally, the GGA+U calculated single crystal elastic constant values decrease continuously with decreasing O/Pu ratio from 2.0 to 1.5. The rate of decrease of the average C11 is almost 11-15 times higher compared to the rate of decrease of C12 and C44.
Collapse
Affiliation(s)
- P S Ghosh
- Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
| | - A Arya
- Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
| |
Collapse
|
6
|
Pegg JT, Shields AE, Storr MT, Wills AS, Scanlon DO, de Leeuw NH. Magnetic structure of UO2and NpO2by first-principle methods. Phys Chem Chem Phys 2019; 21:760-771. [DOI: 10.1039/c8cp03581d] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The magnetic structure of the actinide dioxides (AnO2) remains a field of intense research. A noncollinear relativistic computational study of the AnO2(An = U, Np) magnetic structure has been completed.
Collapse
Affiliation(s)
- James T. Pegg
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
- Atomic Weapons Establishment (AWE) Plc
| | | | - Mark T. Storr
- Atomic Weapons Establishment (AWE) Plc
- Aldermaston
- Reading
- UK
| | - Andrew S. Wills
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
| | - David O. Scanlon
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
- Diamond Light Source Ltd
| | - Nora H. de Leeuw
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
- Cardiff University
| |
Collapse
|