Anharmonic properties of Li

Taole, S. H.; Glyde, H. R.; Taylor, Roger

doi:10.1103/physrevb.18.2643

Cited by 23 publications

(4 citation statements)

References 25 publications

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“…This yields a set of self-consistent equations for the phonon frequencies and vibrational amplitudes to be solved iteratively. The SCP theory and its modifications were used successfully to evaluate the dynamical properties of both three-dimensional ͑3D͒ crystals [11][12][13][14][15] and plane adsorbed monolayers of atoms. 16 -18 Particularly, the improved self-consistent ͑ISC͒ model, which is the SCH approximation corrected for cubic anharmonicity, provides a satisfactory description of the phonon spectrum 13,19 and thermodynamic properties of the rare gas ͑RGC's͒ [11][12][13]20,21 crystals, except for temperatures near the melting point, where the iteration process shows poor convergence.…”

Section: Introductionmentioning

confidence: 99%

Binary distribution functions of atoms of simple crystals

Karasevskii

Lubashenko

2002

Phys. Rev. B

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We propose a method of statistical description of simple crystals and calculation of their thermodynamic functions and equation of state. The method is based on the derivation of an exact expression for the binary distribution function of atomic displacements and a variational procedure for the determination of an effective constant of the quasielastic bond of atoms of the crystal. For rare gas crystals with Morse and Lennard-Jones potentials, we obtained the equation of state and thermodynamic parameters of the solid-state, which are in agreement with experimental data. We also found that a solid-state instability occurs near the observed melting temperature of the crystal, corresponding to a point above which there is no more an equilibrium effective parameter of the quasielastic bond.

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Section: Introductionmentioning

confidence: 99%

Binary distribution functions of atoms of simple crystals

Karasevskii

Lubashenko

2002

Phys. Rev. B

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“…However, in this case, a small T c (<1 K) is expected for realistic values of the parameters (43). For fcc lithium, this condition is theoretically not present (44) and cannot explain the sudden change in the sign of isotopic shift above 21 GPa. However, in the present case, electronic and structural effects may be entangled.…”

Section: Discussionmentioning

confidence: 99%

High-pressure superconducting phase diagram of ⁶ Li: Isotope effects in dense lithium

Schaeffer

Temple

Bishop

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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We measured the superconducting transition temperature of 6 Li between 16 and 26 GPa, and report the lightest system to exhibit superconductivity to date. The superconducting phase diagram of 6 Li is compared with that of 7 Li through simultaneous measurement in a diamond anvil cell (DAC). Below 21 GPa, Li exhibits a direct (the superconducting coefficient, α, T c ∝ M −α , is positive), but unusually large isotope effect, whereas between 21 and 26 GPa, lithium shows an inverse superconducting isotope effect. The unusual dependence of the superconducting phase diagram of lithium on its atomic mass opens up the question of whether the lattice quantum dynamic effects dominate the low-temperature properties of dense lithium.L ight elements (low Z) and their compounds have been the subject of many recent studies for their potential as hightemperature superconductors (e.g., refs. 1-5). Due to their low mass, the physical properties of the low-Z compounds can be strongly influenced by zero-point effects (lattice quantum dynamics) (6), and mass-related isotope effects may be present in their thermodynamics of vibrational degrees of freedom. Such effects will influence the superconducting properties of these materials. Dependence of superconductivity on isotopic variations of low-Z compounds can be used to probe and determine the magnitude of mass-related effects. This in turn allows better development of models to determine their superconducting properties.Under ambient pressure, lithium is the lightest elemental metallic and superconducting system, and it exhibits one of the highest superconducting transition temperatures of any elemental superconductor under compression (7-11). Despite the large mass difference between the stable isotopes of lithium (∼15%), isotope effects in superconductivity of lithium have not been studied before.In systems with long-range attractive potential, the ratio of lattice zero-point displacements to interatomic distances may increase under compression (increase to the Lindemann ratio at high densities), provided they retain their long-range interactions (12,13). (This is opposed to systems with short-range interactions, e.g., helium, in which the lattice becomes more classical under compression.) In these systems, more deviations from the static lattice behavior are expected at higher densities. At sufficiently low temperatures, where thermal energy is small, lattice quantum dynamics can play a more dominant role in the bulk properties. Sound velocity measurements on stable isotopes of lithium at 77 K and up to 1.6 GPa show that quantum solid effects in lithium, at least in the pressure range studied, do not decrease as a function of pressure (14). Raman spectroscopy studies between 40 and 123 GPa and at 177 K report a reduced isotope effect in high-frequency vibrational modes of Li, which may be related to quantum solid behavior (15). Up to this point, no experiments have reported a comparison of any physical properties of lithium isotopes at low temperatures and high pressures concurren...

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“…The well known anomaly in the branch [~0]T~ may be associated with the volumedependent interionic forces (Finnis, 1974). The anharmonic effects (Taole, Glyde & Taylor, 1978) may also contribute towards this anomaly.…”

Section: Discussionmentioning

confidence: 99%

A non-central Fielek model for lattice vibrations in platinum

Agrawal¹,

Rathore²

1980

Acta Cryst Sect A

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The Fielek model is made simple and more effective by modifying it for (a) purely central and short-range ionic interactions, (b) angular interactions coupling the nearby d shells, (c) easily computable volume interactions and (d) for crystal equilibrium in complicated f.c.c, lattices. The model, involving a minimum number of input data, is tested for its validity in predicting the dispersion relations in platinum.

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Anharmonic properties of Li

Cited by 23 publications

References 25 publications

Binary distribution functions of atoms of simple crystals

Binary distribution functions of atoms of simple crystals

High-pressure superconducting phase diagram of ⁶ Li: Isotope effects in dense lithium

A non-central Fielek model for lattice vibrations in platinum

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Anharmonic properties of Li

Cited by 23 publications

References 25 publications

Binary distribution functions of atoms of simple crystals

Binary distribution functions of atoms of simple crystals

High-pressure superconducting phase diagram of 6 Li: Isotope effects in dense lithium

A non-central Fielek model for lattice vibrations in platinum

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Product

Resources

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High-pressure superconducting phase diagram of ⁶ Li: Isotope effects in dense lithium