Thermo-physical properties of LiH at high pressures by <i>ab initio</i> calculations

Mukherjee, D.; Sahoo, Bijaylaxmi; Joshi, K. D.; Gupta, Satish C.; Sikka, S. K.

doi:10.1063/1.3590150

Cited by 15 publications

(6 citation statements)

References 33 publications

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“…By using all-electron GW approximation, Lèbegue et al 16 argued that the structural transition and metallization in LiH should occur simultaneously at a pressure of 329 GPa. This transition pressure is close to the 313 GPa and 327 GPa calculated by Wang et al 17 and Mukherjee et al, 15 respectively. They employed the GGA and full-potential linearized augmented plane wave (LAPW) method as implemented in WIEN2K package.…”

Section: Introductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

“…With theoretical methods, the pressure-induced B1-B2 structural transition and the insulator-metal transition in LiH at low temperatures [12][13][14][15][16][17][18][19][20] have been extensively investigated. The mechanism of the B1-B2 structural transition 14,15,21 is often interpreted using phonon softening and elastic instability. On the other hand, the insulator-metal transition was shown to occur prior to the B1-B2 transition by both the local density approximation (LDA) and semi-local generalized gradient approximation (GGA).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…Furthermore, these theoretical zero pressure elastic constants are utilized to determine the Debye temperature (h D ) at zero pressure for B1 phase using the following procedure. 26,27 According to Debye model of isotropic solid, the elastic wave has one longitudinal and two degenerate transverse polarizations. The average Debye temperature can be expressed as follows:…”

Section: Resultsmentioning

confidence: 99%

Structural, elastic, and lattice dynamic stability of yttrium selenide (YSe) under pressure: A first principle study

Sahoo

Joshi

Gupta

2014

Journal of Applied Physics

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Ab initio calculations on structural, elastic and dynamic stability of CdO at high pressures J. Appl. Phys. 112, 093523 (2012); 10.1063/1.4764899First-principles investigations of elastic stability and electronic structure of cubic platinum carbide under pressure Structural, elastic, and lattice dynamical stability of YSe has been investigated as a function of pressure through first principles electronic band structure calculations. The comparison of enthalpies of rocksalt type (B1) and CsCl type cubic (B2) structures determined as a function of pressure suggests that the B1 phase will transform to B2 structure at $32 (30 GPa at 300 K obtained from comparison of Gibbs free energy at 300 K). The transition is identified to be of first order in nature with a volume discontinuity of $6.2% at the transition pressure. Furthermore, the theoretically determined equation of state has been utilized to derive various physical quantities, such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus. The single crystal elastic constants have been predicted at various pressures for both the B1 and B2 structures using the energy strain method. The activation barrier between B1 and B2 phases calculated at transition point is $19.7mRy/formula unit. Our lattice dynamic calculations show that both the B1 as well as B2 structures are lattice dynamically stable not only at ambient pressure but also at transition pressure. The B1 phase becomes lattice dynamically unstable at $112 GPa, i.e., much beyond the transition pressure. The effect of temperature on volume and bulk modulus of the YSe in B1 phase has also been examined. V C 2014 AIP Publishing LLC.

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“…An accurate description of the properties of this compound also serves as a benchmark for theoretical models due to its simple electronic structure and the influence of zero-point motion on its high-pressure equation of state (EOS) [3]. For example, the conditions for an expected structural and electronic transformation in the solid phase differ widely depending on the electron correlation model chosen by various density functional theory (DFT) simulations [4]. Models for the equation of state in the plasma phase also differ depending on their treatment of the electron, ion and thermal contributions to the free energy, and there are very few experiments constraining these models above a few hundred gigapascals.…”

Section: Introductionmentioning

confidence: 99%

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

Cited by 15 publications

References 33 publications

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

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

Structural, elastic, and lattice dynamic stability of yttrium selenide (YSe) under pressure: A first principle study

Shock equation of state of LiH6 to 1.1 TPa

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