Electronic structure and superconductivity of europium

Nixon, Lane W.; Papaconstantopoulos, D. A.

doi:10.1016/j.physc.2010.07.004

Cited by 5 publications

(2 citation statements)

References 28 publications

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“…However, as we proceed from Ce to Tm, E F is within the very narrow f-bands and as a result DFT cannot find the appropriate minimum of the total energy. We have found that a reasonable equilibrium volume can be calculated for these materials by pushing the f-electrons into the core and use only the s-and d-electrons in the valence [17] [18]. For Yb and La the f-bands are clearly below E F and the calculated equilibrium volume is reasonable.…”

Section: Lanthanides (Yb and La)mentioning

confidence: 84%

Extension of the NRL tight-binding method to include f orbitals and applications in Th, Ac, La and Yb

Durgavich

Sayed

Papaconstantopoulos

2016

Computational Materials Science

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The original Naval Research Laboratory Tight-Binding(NRL-TB) methodology was designed to only include s, p, and d orbitals inthe basis. Because of this limitation, materials which have f orbitals in their valence bands could not be modeled by the current program. In this work we have expanded the NRL-TB method to account for f orbital interactions and used the modified program to investigate Thorium, Actinium, Lanthanum and Ytterbium, materials whose properties are influenced by f electrons. Using the improved program, we were able to develop a set of Slater-Koster polynomial coefficients for these materials that accurately compute properties such as total energy (fcc, bcc, sc, hcp, and diamond), energy bands, density of states, elastic constants, and phonon frequencies.

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Section: Lanthanides (Yb and La)mentioning

confidence: 84%

Extension of the NRL tight-binding method to include f orbitals and applications in Th, Ac, La and Yb

Durgavich

Sayed

Papaconstantopoulos

2016

Computational Materials Science

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“…We note that Nixon and Papaconstantopoulos [22] have recently calculated the electronic structure of Eu for the bcc, hcp, and fcc structures to 90 GPa pressure using the augmented-plane-wave method in the local-density approximation. Using a simple Debye model to approximate the change in the average phonon frequency under pressure, they find that in both the bcc and hcp phases Eu becomes superconducting above 60 GPa, increasing to a value near 2 K at 80 GPa, in agreement with experiment [14].…”

Section: Results Of Structure Searchmentioning

confidence: 99%

Pressure-induced structural transitions in europium to 92 GPa

Meng

Kumar

et al. 2011

Phys. Rev. B

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Synchrotron x-ray diffraction experiments have been carried out on Eu metal at ambient temperature to pressures as high as 92 GPa (0.92 Mbar). Following the well-known bcc-to-hcp transition at 12 GPa, a mixed phase region is observed from 18 to 66 GPa until finally a single orthorhombic (Pnma) phase persists from 66 to 92 GPa. These results are compared to predictions from density functional theory calculations. Under pressure the relatively large molar volume V mol of divalent Eu is rapidly diminished, equaling or falling below V mol (P) for neighboring trivalent lanthanides above 15 GPa. The present results suggest that above 15 GPa Eu is neither divalent nor fully trivalent to pressures as high as 92 GPa. I. IntroductionIn contrast to the other lanthanide metals, which are trivalent, Eu and Yb retain the divalency of their free-atom state. As a result, their atomic volumes are significantly larger and their structures do not fit into the normal structure sequence across the trivalent lanthanide series (hcp → Sm-type → double hcp → fcc → distorted fcc) either with increasing pressure or decreasing atomic number [1][2][3]. At pressures near 1 Mbar, Yb takes on the hexagonal hP3 structure exhibited by the light actinides Sm and Nd under pressure, providing evidence that for pressures of 1 Mbar and above Yb has joined the regular lanthanide series and become fully trivalent [4]. The equation of state (EOS) of Yb is consistent with this conclusion [4].Structure studies on Eu metal at ambient temperatures, on the other hand, have only been carried out to 43 GPa [5,6], revealing a bcc-to-hcp transition at 12 GPa accompanied by a 4% volume collapse, with a new close-packed structure appearing near 17 GPa. From the fact that the EOS of Eu approaches that of trivalent Gd near 20 GPa, it was concluded that at this pressure a significant increase in Eu's valence must have occurred [5]. L III absorption [7] and Mössbauer effect [8,9] studies reportedly indicate that at 10 GPa Eu's valence has already increased to approximately 2.5, with a further increase to 2.64 at pressures of 34 GPa. Theoretical predictions of the pressure necessary for the full divalent-to-trivalent transition in Eu vary from 35 GPa [2, 10] to 71 GPa [11].Should sufficiently high pressure be applied to bring Eu to full trivalency Eu 3+ (4f 6 where J

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Lanthanides

Papaconstantopoulos¹

2014

Handbook of the Band Structure of Elemental Solids

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Electronic structure and superconductivity of europium

Cited by 5 publications

References 28 publications

Extension of the NRL tight-binding method to include f orbitals and applications in Th, Ac, La and Yb

Extension of the NRL tight-binding method to include f orbitals and applications in Th, Ac, La and Yb

Pressure-induced structural transitions in europium to 92 GPa

Lanthanides

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