LiH under high pressure and high temperature: A first‐principles study

Wang, Y.; Ahuja, Rajeev; Johansson, Börje

doi:10.1002/pssb.200301604

Cited by 18 publications

(16 citation statements)

References 11 publications

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“…The corresponding pressure is $ 327 GPa. This is in accord with the predictions of Wang et al 2 and Zurek et al 19 and not with Gou et al 17 and Zhang et al 18 The calculated 300 K isotherm is plotted in Fig. 2 along with the experimental data.…”

Section: Resultssupporting

confidence: 88%

“…As far as structural stability of this compound under high pressure is concerned, widely differing results have been reported in literature. 1,2,[16][17][18][19] On the basis of psuedopotential calculations within local density approximation (LDA), Martins 16 predicted NaCl type (B1 phase) to CsCl type (B2 phase) structural phase transition at $ 450 GPa, whereas, theoretical calculations by Gou et al 17 using ionic overlap compression model found this transition to occur at $ 85 GPa. In contrast to this, the x-ray diffraction measurements in DAC carried out by Loubeyre et al 10 do not show any phase transition up to 94 GPa.…”

Section: Introductionmentioning

confidence: 99%

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Thermo-physical properties of LiH at high pressures by ab initio calculations

Mukherjee

Sahoo

Joshi

et al. 2011

Journal of Applied Physics

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First principles calculations have been carried out to analyze structural stability and to determine the equation of state and elastic constants of LiH as a function of pressure. The comparison of total energies of B1 and B2 structures determined as a function of compression suggests the B1 ! B2 transition at $ 327 GPa. Various physical quantities including zero pressure equilibrium volume, bulk modulus, pressure derivative of bulk modulus, Debye temperature, bulk sound speed, Hugoniot parameter 's' and Gruneisen parameter have been derived. All these physical quantities compare well with the available experimental data. The single crystal elastic constants have been evaluated up to the B1!B2 transition pressure.

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Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Thermo-physical properties of LiH at high pressures by ab initio calculations

Mukherjee

Sahoo

Joshi

et al. 2011

Journal of Applied Physics

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“…At high pressures, the slight deviation between 2DM results and the experimental data might be due to the anharmonicity that was not included in our first-principles QHA calculations, as implied by the QTB-MD 24 calculations.Moreover, we also investigate the isotopic effects on the B1-B2 solid phase boundaries of lithium hydrides. Previous theoretical studies mainly focused on this transition of 7 LiH at 0 and 300 K, and estimated a transition pressure spanning from 200 to 500 GPa[9][10][11][12][13][14][15][16] .The finite temperature phase transition and isotopic effects, however, are not explored. The calculated B1-B2 solid phase boundaries of 6 LiH,6 LiD,6 LiT, and 7 LiT are displayed inFig.…”

mentioning

confidence: 99%

Compression and phase diagram of lithium hydrides at elevated pressures and temperatures by first-principles calculation

Chen¹,

Chen²,

Wu³

et al. 2016

J. Phys. D: Appl. Phys.

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High pressure and high temperature properties of AB (A = 6 Li, 7 Li; B = H, D, T) are investigated with first-principles method comprehensively. It is found that the H − sublattice features in the lowpressure electronic structure near the Fermi level of LiH are shifted to that dominated by the Li + sublattice in compression. The lattice dynamics is studied in quasi-harmonic approximation, from which the phonon contribution to the free energy and the isotopic effects are accurately modelled with the aid of a parameterized double-Debye model. The obtained equation of state (EOS) matches perfectly with available static experimental data. The calculated principal Hugoniot is also in accordance with that derived from shock wave experiments. Using the calculated principal Hugoniot and the previous theoretical melting curve, we predict a shock melting point at 56 GPa and 1923 K. In order to establish the phase diagram for LiH, the phase boundaries between the B1 and B2 solid phases are explored. The B1-B2-liquid triple point is determined at about 241GPa and 2413 K. The remarkable shift in the phase boundaries by isotopic effect and temperature reveal the significant role played by lattice vibrations. Furthermore, the Hugoniot of the staticdynamic coupling compression is assessed. Our EOS suggests that a precompression of the sample to 50 GPa will allow the shock Hugoniot passing through the triple point and entering the B2 solid phase. This transition leads to a discontinuity with 4.6% volume collapse, about four times greater than the same B1-B2 transition at zero temperature.PACS numbers: 63.20.dk, 64.60.A-, 64.70.D-As the lightest ionic compound, as well as the highest mass content of hydrogen and the highest melting point of 965 K at ambient pressure 1 in alkali metal hydrides, LiH has been widely studied and applied in the fields of hydrogen storage 2 , thermonuclear fusion, and aviation and space industries 3-6 . Early static compression experiment using diamond anvil cell (DAC) showed that LiH occupies an FCC lattice and orders in NaCl (B1) structure at ambient condition, and this structure is maintained up to at least 36 GPa (96 GPa for LiD) 7 . Under this pressure, all other alkali hydrides were observed to transform into CsCl (B2) phase (NaH at 29.3 GPa, KH at 4.0 GPa, RbH at 2.2 GPa, CsH at 0.83 GPa) 8-10 . However, the same structural transition in LiH has yet to be observed, which stimulates broad and continuous high pressure experimental and theoretical researches. Recently, by analyzing the x-ray diffraction (XRD) data obtained in DAC experiment 11 , it was shown that at room temperature LiH remains in the B1 structure under pressures up to 252 GPa, the highest pressure having been studied experimentally so far. In particular, the diffraction and Raman data indicated that the B1-B2 phase transition, as well as the accompanied metallization, may not be far beyond 252 GPa 11 .With theoretical methods, the pressure-induced B1-B2 structural transition and the insulator-metal transition in LiH at low temperat...

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“…9. Experimental results compared to previous measurements from the Z machine [51], from gas guns [38] and from underground tests [39,53]; theoretical predictions from QMD (this work, in close agreement with [51,52,58] and density functional theory [59]; and tabulated equation of state models [58,61]. Precompressed data points are shown as diamondshaped red symbols FIG.…”

Section: Resultsmentioning

confidence: 61%

Shock equation of state of LiH6 to 1.1 TPa

et al. 2017

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Using laser-generated shock waves, we have measured pressure, density and temperature of LiH on the principal Hugoniot between 260 and 1100 GPa (2.6-11 Mbar) and on a second-shock Hugoniot up to 1400 GPa to near 5-fold compression, extending the maximum pressure reached in non-nuclear experiments by a factor of two. We observe the onset of metal-like reflectivity consistent with temperature-induced ionization of the Li 2s electron, and no sign of additional changes in ionization up to the maximum pressure. Our measurements are in good agreement with gas gun, Z-machine and underground test data and are accurately described by quantum molecular dynamics simulations. The results confirm the validity of equation of state models built on an average-atom description of the electron-thermal contribution to the free energy and a density-dependent Grüneisen parameter to describe shock response of LiH over this pressure range.

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LiH under high pressure and high temperature: A first‐principles study

Cited by 18 publications

References 11 publications

Thermo-physical properties of LiH at high pressures by ab initio calculations

Thermo-physical properties of LiH at high pressures by ab initio calculations

Compression and phase diagram of lithium hydrides at elevated pressures and temperatures by first-principles calculation

Shock equation of state of LiH6 to 1.1 TPa

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