<i>Ab-initio</i> Calculations of Lattice Dynamics and Superconductivity in FCC Lithium and Iodine and BCC Tellurium

Maheswari, S.; Nagara, Hitose; Kusakabe, Koichi; Suzuki, N.

doi:10.1143/jpsj.74.3227

Cited by 20 publications

(23 citation statements)

References 23 publications

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“…Theoretical works on pressure-induced superconductivity so far, however, have focused on the fcc phase only. [26][27][28][29][30][31][32][33][34][35][36][37] The only exception is the study on fcc and cI16 by Christensen and Novikov 26 based on a rigid muffintin approximation-which proved to be inadequate for Li ͑Ref. 34͒-and without calculation of the phonon spectra for cI16.…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in lithium under high pressure investigated with density functional and Eliashberg theory

et al. 2009

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Structural phase transitions and superconducting properties in three phases ͑9R, fcc, and cI16͒ of solid Li are investigated using a pseudopotential plane-wave method based on density functional perturbation theory. In particular, it is shown that phonon softening is responsible for a pressure-induced fcc→ cI16 transition as well as for a significant enhancement of electron-phonon coupling and superconducting transition temperature T c preceding this structural transformation. The nature of superconductivity in the fcc and cI16 phases is examined by solving the Eliashberg equations with the spectral function ␣ 2 F͑͒ obtained from first-principles calculations and by evaluating the functional derivative ␦T c / ␦␣ 2 F͑͒. The calculated T c reaches a maximum at pressure close to the fcc→ cI16 transition and is significantly reduced in the cI16 phase, in agreement with the trend observed experimentally. The variation in T c as a function of pressure is explained in terms of the functional derivative and shifts of the spectral weight.

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Section: Introductionmentioning

confidence: 99%

Superconductivity in lithium under high pressure investigated with density functional and Eliashberg theory

et al. 2009

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“…Experimental evidence [3][4][5][6][7]9 shows that in the pressure and temperature ranges where the anomalous isotope effect was measured (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) GPa and below 30 K) lithium presents a fcc structure. At around 40 GPa, it transforms to the rhombohedral hR1 phase, which is just a distortion of the fcc phase along the c axis if one switches to a hexagonal representation.…”

Section: Introductionmentioning

confidence: 92%

“…Theoretical calculations within the harmonic approximation in fcc lithium show a highly softened transverse acoustic mode in the ΓK high-symmetry line 13,[18][19][20][21] . Around q inst = 2π/a(2/3, 2/3, 0), where a is the lattice parameter, this anomalous mode presents a huge electron-phonon coupling, becoming a key factor to explain the high T c observed in lithium [18][19][20] .…”

Section: Introductionmentioning

confidence: 97%

Anharmonicity and the isotope effect in superconducting lithium at high pressures: A first-principles approach

et al. 2017

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Recent experiments1 have shown that lithium presents an extremely anomalous isotope effect in the 15-25 GPa pressure range. In this article we have calculated the anharmonic phonon dispersion of 7 Li and 6 Li under pressure, their superconducting transition temperatures, and the associated isotope effect. We have found a huge anharmonic renormalization of a transverse acoustic soft mode along ΓK in the fcc phase, the expected structure at the pressure range of interest. In fact, the anharmonic correction dynamically stabilizes the fcc phase above 25 GPa. However, we have not found any anomalous scaling of the superconducting temperature with the isotopic mass. Additionally, we have also analyzed whether the two lithium isotopes adopting different structures could explain the observed anomalous behavior. According to our enthalpy calculations including zero-point motion and anharmonicity it would not be possible in a stable regime.

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“…At qinst=2π/a(2/3,2/3,0), this anomalous mode presents a huge electron-phonon coupling, becoming a key factor to explain the high Tc observed in lithium [12,14,16]. This softening is associated to a well-defined Fermi surface nesting [14,17] and even yields imaginary phonon frequencies at pressures where fcc is known to be stable; the instability emerges at pressures higher than 30 GPa in the local density approximation, and at even lower pressures if one uses the generalized gradient approximation.…”

Section: Introductionmentioning

confidence: 99%

Dynamical stability of face centered cubic lithium at 25 GPa

Borinaga¹,

Aseginolaza²,

Errea³

et al. 2017

Proc. 17th Int. Conf. On High Pressure in Semiconductor Physics &Amp; Workshop on High-Pressure Study on Superconducting

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We study the dynamical stability of face centered cubic lithium at 25 GPa within ab initio density functional theory calculations. The system shows an extremely softened transverse acoustic mode in the Γ-K high symmetry line, whose frequency is difficult to converge within a first-principles harmonic approach. We estimate the anharmonic correction of this value within the frozen phonon approximation assuming that the transverse acoustic mode only interacts with itself. By solving the Schrödinger equation for the potential energy curve and displacements along the vibrational mode of interest, we obtain the anharmonic eigenvalues and eigenfunctions. While the harmonic approach yields a phonon frequency of -28.6 cm -1 for this mode, anharmonicity renormalizes dramatically this value up to 115.3 cm -1 . Thus, anharmonic effects seem to dynamically stabilize this system.

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Ab-initio Calculations of Lattice Dynamics and Superconductivity in FCC Lithium and Iodine and BCC Tellurium

Cited by 20 publications

References 23 publications

Superconductivity in lithium under high pressure investigated with density functional and Eliashberg theory

Superconductivity in lithium under high pressure investigated with density functional and Eliashberg theory

Anharmonicity and the isotope effect in superconducting lithium at high pressures: A first-principles approach

Dynamical stability of face centered cubic lithium at 25 GPa

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