Static strengths of Ta and U under ultrahigh pressures

Weir, Samuel T.; Akella, Jagannadham; Ruddle, C.; Goodwin, T.J.; Hsiung, L.M.

doi:10.1103/physrevb.58.11258

Cited by 40 publications

(40 citation statements)

References 14 publications

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“…As was mentioned above, tantalum possesses the BCC structure at ambient conditions and this structure remains stable up to at least 1.74 Mbar [42,43]. Söderlind and Moriarty [41] have shown that tantalum is regarded as a good example for demonstrating the successful applications of DFT to the structural stability of the transition metal up to 10 Mbar-the calculated cold EOS for BCC Ta is in an acceptable agreement with DAC experiments up to 0.75 Mbar and with reduced shock data up to 2.3 Mbar.…”

Section: Strength and Elasticity Of Nb And Tamentioning

confidence: 71%

“…For Ta (which remains an ambient pressure BCC structure up to 1.74 Mbar [42,43]), T c changes little from the ambient pressure value of 4.4 K to 450 kbar with the absence of the ETT proposed for Nb by Struzhkin et al [40]. It is worth mentioning that Diamond Anvil Cell (DAC) measurements by Weir et al [42] (the pressure gradient method) have not found any softening in the yield stress up to 1 Mbar pressure.…”

Section: Early Search For Phase Transformations In V Nb and Tamentioning

confidence: 95%

“…It is worth mentioning that Diamond Anvil Cell (DAC) measurements by Weir et al [42] (the pressure gradient method) have not found any softening in the yield stress up to 1 Mbar pressure.…”

Section: Early Search For Phase Transformations In V Nb and Tamentioning

confidence: 98%

“…Tantalum is often used for testing purposes, for study of yield strength, and for comparing theoretical predictions of elastic and plastic properties under extreme pressure and temperatures [41][42][43]50,[54][55][56]58,73,83,84,87,88]. As was mentioned above, tantalum possesses the BCC structure at ambient conditions and this structure remains stable up to at least 1.74 Mbar [42,43].…”

Section: Strength and Elasticity Of Nb And Tamentioning

confidence: 99%

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Kohn Anomaly and Phase Stability in Group VB Transition Metals

et al. 2018

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Abstract:In the periodic table, only a few pure metals exhibit lattice or magnetic instabilities associated with Fermi surface nesting, the classical examples being α-U and Cr. Whereas α-U displays a strong Kohn anomaly in the phonon spectrum that ultimately leads to the formation of charge density waves (CDWs), Cr is known for its nesting-induced spin density waves (SDWs). Recently, it has become clear that a pronounced Kohn anomaly and the corresponding softening in the elastic constants is also the key factor that controls structural transformations and mechanical properties in compressed group VB metals-materials with relatively high superconducting critical temperatures. This article reviews the current understanding of the structural and mechanical behavior of these metals under pressure with an introduction to the concept of the Kohn anomaly and how it is related to the important concept of Peierls instability. We review both experimental and theoretical results showing different manifestations of the Kohn anomaly in the transverse acoustic phonon mode TA (ξ00) in V, Nb, and Ta. Specifically, in V the anomaly triggers a structural transition to a rhombohedral phase, whereas in Nb and Ta it leads to an anomalous reduction in yield strength.

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Section: Strength and Elasticity Of Nb And Tamentioning

confidence: 71%

Section: Early Search For Phase Transformations In V Nb and Tamentioning

confidence: 95%

“…It is worth mentioning that Diamond Anvil Cell (DAC) measurements by Weir et al [42] (the pressure gradient method) have not found any softening in the yield stress up to 1 Mbar pressure.…”

Section: Early Search For Phase Transformations In V Nb and Tamentioning

confidence: 98%

Section: Strength and Elasticity Of Nb And Tamentioning

confidence: 99%

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Kohn Anomaly and Phase Stability in Group VB Transition Metals

et al. 2018

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“…The extreme stability of α-U due to delocalized and strongly bonding 5f electrons is clearly illustrated by the diamond-anvil-cell studies by Akella et al (1997), Weir et al (1998), and Le . In these experiments, α-U is pressurized to 100 GPa, revealing no change in the orthorhombic Cmcm crystal structure and only a relaxation of the orthorhombic axial ratios.…”

Section: Why Does U Metal Exhibit Ls Coupling?mentioning

confidence: 97%

Nature of the5fstates in actinide metals

2009

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Actinide elements produce a plethora of interesting physical behaviors due to the 5f states. This review compiles and analyzes progress in understanding of the electronic and magnetic structure of the 5f states in actinide metals. Particular interest is given to electron energy-loss spectroscopy and many-electron atomic spectral calculations, since there is now an appreciable library of core d → valence f transitions for Th, U, Np, Pu, Am, and Cm. These results are interwoven and discussed against published experimental data, such as x-ray photoemission and absorption spectroscopy, transport measurements, and electron, x-ray, and neutron diffraction, as well as theoretical results, such as density-functional theory and dynamical mean-field theory.

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Large elastoplasticity under static megabar pressures: Formulation and application to compression of samples in diamond anvil cells

Feng

Levitas

Hemley

2016

International Journal of Plasticity

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In high pressure research, static megabar pressures are typically produced by compression of a thin sample by two diamonds in various types of diamond anvil cells. This process is accompanied by large plastic deformation (sample thickness is reduced by a factor of 30), and finite elastic deformation of a sample and even the diamond. A thermodynamically consistent system of equations for large elastic and plastic deformation of an isotropic material obeying nonlinear elasticity and pressure dependent yield condition is formulated. The Murnaghan elasticity law and pressure-dependent J2 plasticity are utilized. The finite-strain third-order elasticity law for cubic crystals is utilized for diamond. A computational algorithm is presented with emphasis on the stress update procedure and derivation of the consistent tangent moduli. It is implemented as a user material subroutine in the finite element code ABAQUS. Material parameters for a rhenium sample, as an example, and a diamond are calibrated based on the experimental and atomistic simulation results in the literature. The evolution of the stress and strain tensor fields in the sample and diamond is studied up to a pressure of 300 GPa. Good correspondence between numerical and experimental pressure distributions at the diamond-sample contact surface is obtained. Because there is a significant scatter of the magnitude of reported third-order single-crystal elastic moduli for diamond, their effect on strains and stresses is studied in detail. With the smaller third-order elastic moduli, the phenomenon of cupping of the diamond-sample contact surface is reproduced, which plays an important role in increasing maximum pressures for a given anvil geometry. The results provide important insight into the mechanical response in diamond anvil cells, interpretation of materials properties under extreme conditions from heterogeneous fields, and

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Static strengths of Ta and U under ultrahigh pressures

Cited by 40 publications

References 14 publications

Kohn Anomaly and Phase Stability in Group VB Transition Metals

Kohn Anomaly and Phase Stability in Group VB Transition Metals

Nature of the5fstates in actinide metals

Large elastoplasticity under static megabar pressures: Formulation and application to compression of samples in diamond anvil cells

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