Anomalous resistivity of lithium at high dynamic pressure

Фортов, В. Е.; Yakushev, V. V.; Kagan, K. L.; Ломоносов, И. В.; Postnov, V. I.; Yakusheva, T. I.; Kuryanchik, A. N.

doi:10.1134/1.1429998

Cited by 17 publications

(13 citation statements)

References 2 publications

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“…However, calculations have suggested that semimetallic or even semiconducting behavior might occur at high pressures [2]. Increases in the electrical resistance of highly compressed Li have also been observed in shockwave experiments, lending support to this suggestion [13,14].The lack of experimental information on the highpressure phases of Li beyond I 43d, the possibility of semiconducting behavior at high pressures, and differences between the various theoretical predictions motivates the present study. We have searched for candidate highpressure phases of Li using a combination of ab initio calculations and ''random structure searching'' which we refer to as ''AIRSS''.…”

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Dense Low-Coordination Phases of Lithium

Pickard

Needs²

2009

Phys. Rev. Lett.

109

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Ab initio density-functional-theory calculations and a structure-searching technique are used to identify candidate high-pressure phases of lithium (Li). We predict threefold coordinated structures to be stable in the pressure range 40-450 GPa and fourfold structures at higher pressures. We describe these lowcoordination phases as elemental electrides. All of the stable phases are metallic but the Cmca-24 structure, and two distortions of it which are marginally the most stable in the pressure range 86-106 GPa, are nearly semiconducting with densities of electronic states at the Fermi energy of only a few percent of the free-electron value. DOI: 10.1103/PhysRevLett.102.146401 PACS numbers: 71.15.Nc, 61.66.Àf, 62.50.Àp In the close-packed structures adopted by Li at low pressures [1] the 2s electrons combine to form a half-filled nearly-free-electron band, consistent with the picture of a simple alkali metal. However, strong deviations from the canonical picture develop at higher pressures. Overlap of the Li 1s core electrons on neighboring atoms under strong compression has a profound effect upon the structures, which adopt lower coordination structures [2,3].The close-packed face-centered-cubic (fcc) phase of Li transforms to a structure of I 43d space group symmetry [4] at $40 GPa, via an intermediate phase of R 3m symmetry [3]. The R 3m phase has a distorted fcc structure, but the I 43d structure departs very substantially from close packing. I 43d has three short interatomic distances giving threefold coordination. Calculations show that the valence electronic density of states (e-DOS) dips around the Fermi energy (E F ) [3]. These features are consistent with the picture that reduced coordination numbers at high pressures arise from a Jahn-Teller-like distortion [2]. Calculations of the high-pressure phases also show an accumulation of electronic charge density within the interstitial region as the 2s electron density is pushed away from the atomic cores by Coulomb repulsion, Pauli exclusion, and the orthogonality of core and valence orbitals [2,3,5].Experiments suggest another phase transition at 60-70 GPa, although the new structure has not been determined [6,7]. A number of theoretical studies have sought to identify candidate phases at higher pressures [2,8,9]. A DFT study by Rousseau et al.[8] found a structure of Cmca symmetry to be more stable than I 43d above 88 GPa. This structure is named Cmca-24, appending the number of atoms in the conventional unit cell [8]. Cmca-24 consists of threefold coordinated atoms [8].Ma et al.[9] studied high-pressure phases of Li using a combination of ab initio DFT methods and an evolutionary search algorithm, finding a new structure of P4 1 32 symmetry which they calculated to be more stable than Cmca-24 above 300 GPa. This structure contains sixfold coordinated atoms. On the other hand, recent hightemperature DFT molecular dynamics simulations found fourfold coordinated Li atoms in the pressure range 150-810 GPa [10].Superconductivity has been observed in Li up...

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confidence: 60%

Dense Low-Coordination Phases of Lithium

Pickard

Needs²

2009

Phys. Rev. Lett.

109

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“…The comparison with Li (Fig. 2) demonstrates that the peak in P n (t) of Li is much higher, indicating significantly stronger inter- [14,15]. The data from [14] are divided into two sets, representing two temperature intervals.…”

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“…2) demonstrates that the peak in P n (t) of Li is much higher, indicating significantly stronger inter- [14,15]. The data from [14] are divided into two sets, representing two temperature intervals. Only qualitative comparison is meaningful with [14] as a model equation of state has been used there to obtain Li density, T , and σ.…”

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Tetrahedral Clustering in Molten Lithium under Pressure

2008

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A series of electronic and structural transitions are predicted in molten lithium from first principles. A new phase with tetrahedral local order characteristic of sp3 bonded materials and poor electrical conductivity is found at pressures above 150 GPa and temperatures as high as 1000 K. Despite the lack of covalent bonding, weakly bound tetrahedral clusters with finite lifetimes are predicted to exist. The stabilization of this phase in lithium involves a unique mechanism of strong electron localization in interstitial regions and interactions among core electrons. The calculations provide evidence for anomalous melting above 20 GPa, with a melting temperature decreasing below 300 K, and point towards the existence of novel low-symmetry crystalline phases.

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“…The high-pressure phases of Li-cI16, Rb-oC52, and Cs-oC84 [21,22,23] thus should be considered as Hume-Rothery phases, similar to the classical Cu-Zn alloy phases. At compression, Li shows an increase in resistivity at high temperatures [24] and an appearance and increase of superconductivity. [25,26,27] The reason for these is probably connected with the enhancement of the Hume-Rothery effect at high pressure.…”

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Stability of hume-rothery phases in Cu−Zn alloys at pressures up to 50 GPa

Degtyareva

Sakharov

Novokhatskaya

et al. 2006

Metall Mater Trans A

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The crystal structure of the g-brass phase Cu 5 Zn 8 is confirmed with single-crystal X-ray diffraction and a charge-coupled device (CCD) detector to be cubic with 52 atoms in the unit cell, space group I 43m, and the refined atomic positions are in good agreement with previously reported data. The structural behavior of a-(fcc), b-(bcc), and g-brass (cI52) phases of the Cu-Zn alloy system has been studied under pressure using diamond anvil cells and powder X-ray diffraction with synchrotron radiation. The appearance of additional peaks in the diffraction patterns of aand b-phases indicates the beginning of transitions to new phases at 17 and 37 GPa, respectively. The complex cubic g-brass phase (52 atoms in the unit cell, space group I 43m) is observed to be stable up to at least 50 GPa. The bulk modulus K 0 was determined as 140(4) GPa for a-, 139(5) for b-, and 121(2) for g-phase assuming K 0 9 5 4. The structural stability of brass phases of the Cu-Zn system under pressure is discussed in terms of the Hume-Rothery mechanism.

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Anomalous resistivity of lithium at high dynamic pressure

Cited by 17 publications

References 2 publications

Dense Low-Coordination Phases of Lithium

Dense Low-Coordination Phases of Lithium

Tetrahedral Clustering in Molten Lithium under Pressure

Stability of hume-rothery phases in Cu−Zn alloys at pressures up to 50 GPa

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