Phase transformations and equation of state of praseodymium metal to 103 GPa

Chesnut, Gary N.; Vohra, Yogesh K.

doi:10.1103/physrevb.62.2965

Cited by 43 publications

(52 citation statements)

References 17 publications

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“…Figure 9 gives the pressure-volume results corresponding to Figs. 6-8, with experimental 300-K data shown for Ce, 1,2,3 Pr, 4,5,6,7 and Nd. 13,68,69 Except for the T = 0 LDA results (thin solid lines), 70 the theoretical results are negative volume derivatives of the 632-K total energies in these figures, an approximation justified by the F exp (300 K) ∼ E exp (632 K) comparisons in Figs.…”

Section: Equation Of Statementioning

confidence: 70%

Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd

McMahan

2005

Phys. Rev. B

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This paper reports calculations for compressed Ce (4f 1 ), Pr (4f 2 ), and Nd (4f 3 ) using a combination of the local-density approximation (LDA) and dynamical mean field theory (DMFT), or LDA+DMFT. The 4f moment, spectra, and the total energy among other properties are examined as functions of volume and atomic number for an assumed face-centered cubic (fcc) structure. These materials are seen to be strongly localized at ambient pressure and for compressions up through the experimentally observed fcc phases (γ phase for Ce), in the sense of having fully formed Hund's rules moments and little 4f spectral weight at the Fermi level. Subsequent compression for all three lanthanides brings about significant deviation of the moments from their Hund's rules values, a growing Kondo resonance at the Fermi level, an associated softening in the total energy, and quenching of the spin orbit since the Kondo resonance is of mixed spin-orbit character while the lower Hubbard band is predominantly j = 5/2. While the most dramatic changes for Ce occur within the two-phase region of the γ-α volume collapse transition, as found in earlier work, those for Pr and Nd occur within the volume range of the experimentally observed distorted fcc (dfcc) phase, which is therefore seen here as transitional and not part of the localized trivalent lanthanide sequence. The experimentally observed collapse to the α-U structure in Pr occurs only on further compression, and no such collapse is found in Nd. These lanthanides start closer to the localized limit for increasing atomic number, and so the theoretical signatures noted above are also offset to smaller volume as well, which is possibly related to the measured systematics of the size of the volume collapse being 15%, 9%, and none for Ce, Pr, and Nd, respectively.

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Section: Equation Of Statementioning

confidence: 70%

Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd

McMahan

2005

Phys. Rev. B

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“…II and III. The volume range studied is from 10 to 50Å 3 /atom which may be compared to 300-K experimental volumes of 14.8, 14.1, and 14.2Å 3 /atom at a pressure of 100 GPa; and 34.4, 34.5, and 34.2Å 3 /atom at 0 GPa; for Ce, 10,52 Pr, 13,52 and Nd, 6,52 respectively. respectively, from Fig.…”

Section: Resultsmentioning

confidence: 99%

“…2,3,4 Transitions in the region between these two limits may exhibit unusually large volume changes. While not the case for Nd, 5,6 the γ-α "volume collapse" of 15% in Ce is well known, 7,8,9,10 and similar collapses occur in Pr (9%), 11,12,13,14,15 Gd (5%), 16 and Dy (6%). 17 Magnetic properties at atmospheric pressure are generally consistent with atomic 4f Hund's rules moments, 4,18 while the susceptibility for the collapsed α-Ce phase 7 and for early actinide analogs 19 is temperature-independent, enhanced Pauli paramagnetic, indicating absent or screened moments.…”

Section: Introductionmentioning

confidence: 99%

Screening of4fmoments and delocalization in the compressed light rare earths

2009

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Spin and charge susceptibilities and the 4f n , 4f n−1 , and 4f n+1 configuration weights are calculated for compressed Ce (n = 1), Pr (n = 2), and Nd (n = 3) metals using dynamical mean field theory combined with the local-density approximation. At ambient and larger volumes these trivalent rare earths are pinned at sharp 4f n configurations, their 4f moments assume atomic-limiting values, are unscreened, and the 4f charge fluctuations are small indicating little f state density near the Fermi level. Under compresssion there is dramatic screening of the moments and an associated increase in both the 4f charge fluctuations and static charge susceptibility. These changes are coincident with growing weights of the 4f n−1 configurations, which it is argued are better measures of delocalization than the 4f n+1 weights which are compromised by an increase in the number of 4f electrons caused by rising 6s, 6p bands. This process is continuous and prolonged as a function of volume, with strikingly similarity among the three rare earths, aside from the effects moderating and shifting to smaller volumes for the heavier members. The observed α-γ collapse in Ce occurs over the large-volume half of this evolution, the Pr analog at smaller volumes, and Nd has no collapse.

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“…The instrumental resolution of the EELS is somewhat broader (σ = 0.35-0.4 eV) in line with expectations, while that of the NIXS is ~1.4 eV FWHM. The total 3d 9 4f n+1 multiplet structure (disregarding selection rules) covers a very broad energy range (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) eV for each spin-orbit split peak-see Thole [48]). However, selection rules greatly reduce the number of final states that can be reached from the initial state.…”

Section: B the M 45 Spectramentioning

confidence: 99%

“…Alloying (chemical substitution), pressure, and temperature can effectively tune the 4f electron localization, turning the eigenstates of the system into admixtures of atomic-like states with corresponding admixtures of f-electron occupancy. In particular, Ce, Pr, and Nd metals exhibit a trend of pressure-driven volume collapses-from large (Ce, 15%) to moderate (Pr, 9%) to none at all (Nd)-related to 4f electron delocalization [3,6,[8][9][10][11][12][13][14][15][16][17][18][19]. The character of this delocalization may be substantially different in each material, and the xray scattering used here promises to be an important probe for relevant high-pressure work.…”

Section: Introductionmentioning

confidence: 99%

Core and shallow-cored- tof-shell excitations in rare-earth metals

et al. 2011

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We report on the results of probing the light lanthanide metals Ce, Pr, and Nd with inelastic x-ray and electron scattering. Transmission electron microscope-based electron spectroscopy and nonresonant inelastic x-ray scattering are shown to be in a high degree of accord, and here serve as complementary probes of electronic structure. The high resolution and high signal-to-noise electron technique allows for the measurement of the complex and subtle excitation spectra in the lanthanide metals, validating the applicability of the screened trivalent atomic model used for these materials. In addition, the momentum transfer dependence of the x-ray scattering is extracted and compared against atomic calculations for the most tightly bound excitonic resonances, which provides a direct test of the predicted atomic radial wave functions.

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Phase transformations and equation of state of praseodymium metal to 103 GPa

Cited by 43 publications

References 17 publications

Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd

Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd

Screening of4fmoments and delocalization in the compressed light rare earths

Core and shallow-cored- tof-shell excitations in rare-earth metals

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