X-ray diffraction and Raman studies of beryllium: Static and elastic properties at high pressures

Evans, W. J.; Lipp, M. J.; Cynn, Hyunchae; Yoo, Choong‐Shik; Somayazulu, Maddury; Häusermann, Daniel M.; Shen, Guoyin; Prakapenka, Vitali B.

doi:10.1103/physrevb.72.094113

Cited by 53 publications

(75 citation statements)

References 40 publications

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“…Near the melting temperature T M (∼ 1, 550 K at 0 GPa), a competing phase with the body-centered cubic symmetry (bcc) seems to emerge [4][5][6]. However, not all experiments [7][8][9][10][11][12][13] have observed this bcc phase, causing confusion and controversies. Be is important for both fundamental research [14][15][16][17] and practical applications.…”

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confidence: 99%

Premelting hcp to bcc Transition in Beryllium

Sun

Zhang

et al. 2017

Phys. Rev. Lett.

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Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp → bcc transition occurs near the melting curve at 0 < P < 11 GPa with a positive Clapeyron slope of 41 ± 4 K/GPa. The bcc phase exists in a narrow temperature range that shrinks with increasing pressure, explaining the difficulty in observing this phase experimentally. This work also demonstrates the validity of this theoretical framework based on phonon quasiparticle to study structural stability and phase transitions in strongly anharmonic materials.PACS numbers: 63.20. Ry, 81.30.Bx, 61.50.Ks,Elemental solids usually undergo a series of phase transitions from ambient conditions to extreme conditions [1][2][3]. Knowledge of their phase diagrams is a prerequisite for establishing their equations of state (EOS), a fundamental relation for determining thermodynamics properties and processes at high pressures and temperatures (PT). However, resolving phase boundaries is challenging for experiments given the uncertainties from several sources, especially at very high PT. Beryllium (Be) is a typical system whose phase diagram remains an open problem despite intense investigations. It assumes a hexagonal close-packed (hcp) structure at relatively low T [1]. Near the melting temperature T M (∼ 1, 550 K at 0 GPa), a competing phase with the body-centered cubic symmetry (bcc) seems to emerge [4][5][6]. However, not all experiments [7][8][9][10][11][12][13] have observed this bcc phase, causing confusion and controversies. Be is important for both fundamental research [14][15][16][17] and practical applications. Being a strong and light-weight metal, it has been widely used in a broad range of technological applications in harsh environments and extreme PT conditions, e.g., up to T > 4,000 K and P > 200 GPa [18][19][20][21][22].The bcc phase of Be was directly observed [4,5] only at T > 1, 500 K around ambient pressure before melting. Measurements of the temperature dependent resistance suggested that bcc Be is a high pressure phase and the hcp/bcc phase boundary between 0 < P < 6 GPa has a negative Clapeyron slope (−52 ± 8 K/GPa) [6]. However, recent experiments have challenged this conclusion [8,9,[11][12][13]. For example, it was reported that bcc Be was not observed for 8 < P < 205 GPa and 300 < T < 4, 000 K [13]. On the theory side, the study of Be's phase diagram using conventional methods encounters significant difficulties. The lattice dynamics of bcc Be is highly anharmonic, and the widely used quasi-harmonic approximation (QHA) and Debye model are not able to capture such effect [23][24][25][26][27][28][29]. For this reason, bcc Be and the associated hcp/bcc phase transition remain poorly understood for P < 11 GPa (density < 2.1g/...

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confidence: 99%

Premelting hcp to bcc Transition in Beryllium

Sun

Zhang

et al. 2017

Phys. Rev. Lett.

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“…Other details of the electronic structure, such as the peak at --15eV in the DOS of the Cmcm--6 phase (which is due to low--lying boron 2s states) are, of course, unique to the LiBeB system. Note that pure beryllium has a high pressure bcc phase that is predicted to be stabilized at around 400GPa [52], and has not been found up to 200GPa [53]. For the isoelectronic LiBeB, the bcc variants discussed here are stabilized at much lower pressures.…”

Section: Is Libeb At High Pressure Similar To Beryllium?mentioning

confidence: 93%

LiBeB: A predicted phase with structural and electronic peculiarities

et al. 2012

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Beginning an in--depth analysis of binaries and ternaries in the Li/Be/B system, we examine the static structures and electronic properties of LiBeB (i.e 1:1:1) over a range of pressures. This as yet unknown compound is predicted to possess a stable ground state at 1 atm and some higher pressures. As the pressure rises, LiBeB goes through a diverse series of structures, beginning with metallic structures which feature chains and layers of atoms, progressing to structures built on "colorings" of the Laves phases, and containing helical arrangements of boron atoms, on to high pressure phases that are ternary variants of a bcc lattice. The density of states (DOS) at the Fermi level consistently falls in a pseudogap (sometimes a real gap is predicted); LiBeB is unlikely to be a good metal or superconductor. The distribution of the DOS follows what electronegativity would predict -Li electrons are 2 transferred to B. Some curious features of the LiBeB structures emerge, these include near--icosahedral coordination, independent of atom type; in a range of pressures a resemblance of the total DOS to that of metallic Be; and also a Dirac surface.3

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“…This approach could create thermal gradients in the sample depending on how good the contact is, however it does not require the ablation coating to be a conductor. In this section, molecular dynamics (MD) calculations are used to examine shock wave propagation along [100], [111], and [110] directions in aluminum single crystals. Four different embedded-atom method (EAM) potentials were used to obtain wave profiles in ideal (defect-free) crystals shocked to peak longitudinal stresses approaching 13 GPa.…”

Section: Appendixmentioning

confidence: 99%

Modeling ramp compression experiments using large-scale molecular dynamics simulation.

Mattsson¹,

Desjarlais²,

Grest³

et al. 2011

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Molecular dynamics simulation (MD) is an invaluable tool for studying problems sensitive to atomscale physics such as structural transitions, discontinuous interfaces, non-equilibrium dynamics, and elastic-plastic deformation. In order to apply this method to modeling of ramp-compression experiments, several challenges must be overcome: accuracy of interatomic potentials, length-and time-scales, and extraction of continuum quantities. We have completed a 3 year LDRD project with the goal of developing molecular dynamics simulation capabilities for modeling the response of materials to ramp compression. The techniques we have developed fall in to three categories (i) molecular dynamics methods (ii) interatomic potentials (iii) calculation of continuum variables. Highlights include the development of an accurate interatomic potential describing shock-melting of Beryllium, a scaling technique for modeling slow ramp compression experiments using fast ramp MD simulations, and a technique for extracting plastic strain from MD simulations. All of these methods have been implemented in Sandia's LAMMPS MD code, ensuring their widespread availability to dynamic materials research at Sandia and elsewhere.3

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X-ray diffraction and Raman studies of beryllium: Static and elastic properties at high pressures

Cited by 53 publications

References 40 publications

Premelting hcp to bcc Transition in Beryllium

Premelting hcp to bcc Transition in Beryllium

LiBeB: A predicted phase with structural and electronic peculiarities

Modeling ramp compression experiments using large-scale molecular dynamics simulation.

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