Quantum effects in condensed matter at high pressure

Стишов, С. М.

doi:10.3367/ufnr.0171.200103c.0299

Cited by 8 publications

(3 citation statements)

References 20 publications

(4 reference statements)

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“…Because the values of Δ C and Δ B are observed to decrease with increasing temperature or pressure [12,16,17], the value of L D (T m ) will be closer to 1/2.…”

Section: Calculations Of the Diffusion Parameters For Diamond And Bccmentioning

confidence: 90%

“…(16) Here, the coefficient Δ D , which defines the isotope shift of the relative coefficient of self-diffusion with increasing X (heavy isotope fraction), is Δ D = = Δ m L D (T) = (Δ m /2) + R D (T). In so doing, it is evident that the first term is independent of temperature, and the second term R D (T) depends on temperature significantly and decreases with increasing T from the value of R D (T = 0 K) >> 1 to zero at T → ∞ (see Tables 2 and 3 and Fig.…”

Section: Given Inmentioning

confidence: 99%

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The behavior of self-diffusion coefficient under conditions of varying isotope composition of crystal

Magomedov

2006

High Temp

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The variation of diffusion parameters with varying isotope composition in both the high-temperature and low-temperature region is studied in view of the dependence of the parameters of interatomic potential on the atomic mass. It is demonstrated that the isotopic dependence of the coefficient of self-diffusion is insignificant at high temperatures. However, upon transition to low temperatures, the difference between the coefficients of self-diffusion in isotopically different crystals becomes appreciable. Calculations for diamond and lithium reveal that the coefficient of self-diffusion in the low-temperature region decreases by one-three orders of magnitude during transition from 12 C to 13 C and increases by an order of magnitude during transition from 7 Li to 6 Li. This effect is associated with quantum tunneling at low temperatures and is caused by the presence of "zero-point oscillations" of atoms. It is demonstrated that, in the high-temperature region, the inclusion of isotopic dependence of the parameters of interatomic potential has a marked effect on the self-diffusion coefficient. The temperature dependence of self-diffusion coefficient is calculated, and temperatures are estimated below which the Arrhenius law is no longer valid.

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“…Because the values of Δ C and Δ B are observed to decrease with increasing temperature or pressure [12,16,17], the value of L D (T m ) will be closer to 1/2.…”

Section: Calculations Of the Diffusion Parameters For Diamond And Bccmentioning

confidence: 90%

Section: Given Inmentioning

confidence: 99%

The behavior of self-diffusion coefficient under conditions of varying isotope composition of crystal

Magomedov

2006

High Temp

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“…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.)…”

mentioning

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 calculation of the parameters of the Mie-Lennard-Jones potential

Magomedov

2006

High Temp

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A method is suggested for self-consistent calculation of the characteristics of interatomic potential of the type of Mie-Lennard-Jones potential, which is based on the lattice parameter, sublimation energy, Debye temperature, and Gr neisen parameter at zero values of temperature and pressure. The method, which takes into complete account the "zero-oscillation" energy, is valid for use with both classical and quantum substances. The results of calculation of the parameters of this potential for Van der Waals crystals demonstrated good agreement with the data of other authors. The parameters of interatomic potential are determined for 70 elements which exhibit the chemical bond of predominantly metallic type. The correlation of the potential parameters with the position of the element in the periodic table is analyzed. The ranges of permitted values of the parameters of the potential are estimated. The parameters of the potential for Rn, T 2 , HD, HT, and DT are predicted, and the values of the Debye temperature, Gr neisen parameter, sublimation energy, molar volume, and of the specific surface energy of {100} face are calculated for these crystals. The variation of the parameters of the potential with the variation of the isotopic composition of crystal is estimated.

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Quantum effects in condensed matter at high pressure

Cited by 8 publications

References 20 publications

The behavior of self-diffusion coefficient under conditions of varying isotope composition of crystal

The behavior of self-diffusion coefficient under conditions of varying isotope composition of crystal

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

The calculation of the parameters of the Mie-Lennard-Jones potential

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Quantum effects in condensed matter at high pressure

Cited by 8 publications

References 20 publications

The behavior of self-diffusion coefficient under conditions of varying isotope composition of crystal

The behavior of self-diffusion coefficient under conditions of varying isotope composition of crystal

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

The calculation of the parameters of the Mie-Lennard-Jones potential

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Product

Resources

About

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