High-pressure Sound Velocity Research Articles

Sound velocity measurement based on laser-induced micro-flyers

The measurement of high-pressure sound velocity in solid materials is crucial for developing constitutive equations and equations of state for materials in extreme stress–strain rate conditions. In this study, we propose a novel method for high-pressure sound velocity measurement using laser-induced micro-flyer technology. By optimizing laser driving conditions and target structure design, we measure high-pressure sound velocity using the “reverse-impact geometry” approach. The well-established Photon Doppler Velocimetry system allows for high-precision, single-shot measurements of both flyer velocity and particle velocity histories. A systematic error analysis shows that the longitudinal sound velocity of aluminum obtained in this experiment is consistent with data from traditional devices, such as gas guns, within the error margin. Finally, we analyze the potential application value of this method in laser technology as well as high-pressure dynamic responses of materials, and conclude the current shortcomings and possible improvements of this method.

The Side-Release Method Measures the High-Pressure Sound Velocity of Iron Using Line-Spatially Resolved DISAR.

The study of high-pressure sound velocity is an important part of shock wave physics, and the study of ultra-high pressure sound velocity of iron is of great significance to many research fields such as geophysics, solid state physics, and crystallography. At present, the measurement of sound velocity is usually carried out by the catch-up sparse wave method and windowed VISAR technology, which is complex in structure and not highly adaptable. In particular, for the ultra-high pressure sonic velocity measurement of metals, it is limited by the loading platform and window materials and cannot realize the high temperature and high-pressure environment of the earth's inner core. In this paper, the sound velocity measurement of iron under high temperature and high-pressure environment (78 GPa) is realized based on the two-stage light gas cannon experimental platform. The side-side sparse wave method was used to establish a coupling model of high-spatially resolved optical group and fiber bundle. A multiplexed all-fiber laser interferometry velocity measurement system (DISAR) was built, and the spatial resolution was better than 20 μm. In this paper, we will provide a feasible route for a method for measuring the high spatiotemporal resolution velocity.

Thermal expansivity and high-pressure sound velocities of natural topaz and implications for seismic velocities and H2O and fluorine recycling in subduction zones

Thermal expansivity and high-pressure sound velocities of natural topaz and implications for seismic velocities and H2O and fluorine recycling in subduction zones

Compression of gaseous hydrogen into warm dense states up to 95 GPa using multishock compression technique

The thermodynamic properties of warm dense hydrogen, such as the equation of state (EOS) and sound velocity, affect our understanding of the evolution and interior structures of gas giant planets. However, for this low-$Z$ gas, obtaining the EOS and sound velocity experimentally under relevant planetary conditions is challenging because the extremely warm states are difficult to reach, characterize, and interrogate. Here, the multishock compression technique is used to generate the thermodynamic states of warm dense hydrogen. This provides a dynamic loading from shock adiabatic to quasi-isentropic compressions, covering wide pressure and density ranges of 0.02--95 GPa and $0.01--0.64 \mathrm{g}/{\mathrm{cm}}^{3}$, which enables us to determine the EOS and infer the high-pressure sound velocities of warm dense hydrogen relevant to planetary interiors. The data obtained in this way are comprehensively compared with several important theoretical models for astrophysics applications. The present experiments provide desirable principal- and off-Hugoniot states for revisiting the thermodynamic space of existing experimental data. These observations and thermodynamic states may be important in guiding future theoretical developments and constructing interior structure models for gas giant planets.

Evidence for mechanical softening-hardening dual anomaly in transition metals from shock-compressed vanadium

Solid usually becomes harder and tougher under compression, and turns softer at elevated temperature. Recently, compression-induced softening and heating-induced hardening (CISHIH) dual anomaly was predicted in group VB elements such as vanadium. Here, the evidence for this counterintuitive phenomenon is reported. By using accurate high-temperature high-pressure sound velocities measured at Hugoniot states generated by shock-waves, together with first-principles calculations, we observe not only the prominent compression-induced sound velocity reduction, but also strong heating-induced sound velocity enhancement, in shocked vanadium. The former corresponds to the softening in shear modulus by compression, whereas the latter reflects the reverse hardening by heat. These experiments also unveil another anomaly in Young's modulus that wasn't reported before. Based on the experimental and theoretical data, we infer that vanadium might transition from BCC into two different rhombohedral (RH1 and RH2) phases at about 79GPa and 116GPa along the Hugoniot, respectively, which implies a dramatic difference in static and dynamic loading, as well as the significance of deviatoric stress and rate-relevant effects in high-pressure phase transition dynamics.

Nonlinear effects of hydration on high-pressure sound velocities of rhyolitic glasses

AbstractAcoustic compressional and shear wave velocities (VP, VS) of anhydrous (AHRG) and hydrous rhyolitic glasses (HRG) containing 3.28 wt% (HRG-3) and 5.90 wt% (HRG-6) total water concentration (H2Ot) have been measured using Brillouin light scattering (BLS) spectroscopy up to 3 GPa in a diamond-anvil cell at ambient temperature. In addition, Fourier-transform infrared (FTIR) spectroscopy was used to measure the speciation of H2O in the glasses up to 3 GPa. At ambient pressure, HRG-3 contains 1.58 (6) wt% hydroxyl groups (OH–) and 1.70 (7) wt% molecular water (H2Om) while HRG-6 contains 1.67 (10) wt% OH– and 4.23 (17) wt% H2Om where the numbers in parentheses are ±1σ. With increasing pressure, very little H2Om, if any, converts to OH– within uncertainties in hydrous rhyolitic glasses such that HRG-6 contains much more H2Om than HRG-3 at all experimental pressures. We observe a nonlinear relationship between high-pressure sound velocities and H2Ot, which is attributed to the distinct effects of each water species on acoustic velocities and elastic moduli of hydrous glasses. Near ambient pressure, depolymerization due to OH– reduces VS and G more than VP and KS. VP and KS in both anhydrous and hydrous glasses decrease with increasing pressure up to ~1–2 GPa before increasing with pressure. Above ~1–2 GPa, VP and KS in both hydrous glasses converge with those in AHRG. In particular, VP in HRG-6 crosses over and becomes higher than VP in AHRG. HRG-6 displays lower VS and G than HRG-3 near ambient pressure, but VS and G in these glasses converge above ~2 GPa. Our results show that hydrous rhyolitic glasses with ~2–4 wt% H2Om can be as incompressible as their anhydrous counterpart above ~1.5 GPa. The nonlinear effects of hydration on high-pressure acoustic velocities and elastic moduli of rhyolitic glasses observed here may provide some insight into the behavior of hydrous silicate melts in felsic magma chambers at depth.

Multishock to Quasi-Isentropic Compression of Dense Gaseous Deuterium-Helium Mixtures up to 120GPa: Probing the Sound Velocities Relevant to Planetary Interiors.

Shock reverberation compression experiments on dense gaseous deuterium-helium mixtures are carried out to provide thermodynamic parameters relevant to the conditions in planetary interiors. The multishock pressures are determined up to 120GPa and reshock temperatures to 7400K. Furthermore, the unique compression path from shock-adiabatic to quasi-isentropic compressions enables a direct estimation of the high-pressure sound velocities in the unexplored range of 50-120GPa. The equation of state and sound velocity provide particular dual perspectives to validate the theoretical models. Our experimental data are found to agree with several equation of state models widely used in astrophysics within the probed pressure range. The current data improve the experimental constraints on sound velocities in the Jovian insulating-to-metallic transition layer.

An experimental method of simultaneously studying refractive index and dynamic properties of transparent materials

Based on the electromagnetic loading device CQ-4, an experimental method of simultaneously measuring the refractive index and high pressure sound velocity of transparent material is established. The ramp wave compression experiment of PMMA is carried out under a pressure of 14 GPa. The velocity history curves of PMMA sample rear surface are obtained by dual laser heterodyne velocimetry (DLHV). The velocity curve shows obvious double wave structure, which indicates the elastic-plastic transition. The refractive index particle velocity optical characteristics and Lagrangian sound velocity particle velocity dynamic characteristics of PMMA are obtained simultaneously with the experimental data processing.

Effects of alkali and alkaline-earth cations on the high-pressure sound velocities of aluminosilicate glasses

The sound velocities (compressional wave velocity [VP] and shear wave velocity [VS]) of four types of aluminosilicate glasses (Mg3Al2Si6O18 (MAS), Ca3Al2Si6O18 (CAS), Na3AlSi3O9 (NAS), and K3AlSi3O9 (KAS)) are measured using the ultrasonic technique at high pressures of up to 7.8 GPa. The VP and VS of MAS glass decrease up to a pressure of 2 GPa and subsequently increase with increasing pressure. The pressure dependence of the CAS glass velocities changes; VP remains almost constant when P ≤ 2 GPa and subsequently increases above 2 GPa. The minimum VS can be observed at approximately 2 GPa, which is similar to that in the case of the MAS glass. The sound velocities of the NAS and KAS glasses monotonically increase with pressure. The increments in the VP and VS of the KAS glass show less sensitivity when compared with that observed in the case of the NAS glass within the pressure range of our experiments. The differences in the properties of the modifying cations in the glasses, such as size ([5]Mg2+ < [~6−7]Ca2+ ≈ [~6−7]Na+ < [~9−11]K+) and field strength (ratio of the charge to the square radius), can be considered responsible for each sound velocity trend. The effects of the cation field strength on the structure and elasticity of the aluminosilicate glasses could govern the pressure-induced change in sound velocities. The results indicate that the type and amount of cation control the elastic behavior of silicate glass under high pressure.

High-pressure structure and elastic properties of tantalum single crystal: First principles investigation**Project supported by the Basic and Frontier Technical Research Project of Henan Province, China (Grant No. 152300410228), the University Innovation Team Project in Henan Province, China (Grant No. 15IRTSTHN004), and the Key Scientific Research Project of Higher Education of Henan Province, China (Grant No. 17A140014).

Since knowledge of the structure and elastic properties of Ta at high pressures is critical for addressing the recent controversies regarding the high-pressure stable phase and elastic properties, we perform a systematical study on the high-pressure structure and elastic properties of the cubic Ta by using the first-principles method. Results show that the initial body-centered cubic phase of Ta remains stable even up to 500 GPa and the high-pressure elastic properties are excellently consistent with the available experimental results. Besides, the high-pressure sound velocities of the single- and poly-crystals Ta are also calculated based on the elastic constants, and the predications exhibit good agreement with the existing experimental data.

Revisit of the relationship between the elastic properties and sound velocities at high pressures

The second-order elastic constants and stress-strain coefficients are defined, respectively, as the second derivatives of the total energy and the first derivative of the stress with respect to strain. Since the Lagrangian and infinitesimal strain are commonly used in the two definitions above, the second-order elastic constants and stress-strain coefficients are separated into two categories, respectively. In general, any of the four physical quantities is employed to characterize the elastic properties of materials without differentiation. Nevertheless, differences may exist among them at non-zero pressures, especially high pressures. Having explored the confusing issue systemically in the present work, we find that the four quantities are indeed different from each other at high pressures and these differences depend on the initial stress applied on materials. Moreover, the various relations between the four quantities depicting elastic properties of materials and high-pressure sound velocities are also derived from the elastic wave equations. As examples, we calculated the high-pressure sound velocities of cubic tantalum and hexagonal rhenium using these nexus. The excellent agreement of our results with available experimental data suggests the general applicability of the relations.

High-pressure sound velocity of PMMA studied by using brillouin spectroscopy

The acoustic properties of poly(methyl methacrylate) (PMMA) were investigated as functions of pressure by using a Fabry-Perot interferometer and a diamond anvil cell. The longitudinal sound velocity was measured for the first time from ambient pressure up to 11 GPa, over which range it changed from 2630 to 7240 m/s upon compression. The rate of change in the sound velocity with respect to pressure exhibited large values in the low-pressure range below about 0.5 GPa and decreased markedly upon further compression at pressures above ∼0.5 GPa. This significant change was tentatively attributed to a substantial decrease in free volume upon applying the pressure. The pressure dependence of the sound velocity did not display any substantial hysteresis between the compression and the decompression processes, but the half width of the Brillouin doublet and the related acoustic attenuation showed some hysteresis, the origin of which remains unclear.

Composition of the Earth's inner core from high-pressure sound velocity measurements in Fe–Ni–Si alloys

We performed room-temperature sound velocity and density measurements on a polycrystalline alloy, Fe0.89Ni0.04Si0.07, in the hexagonal close-packed (hcp) phase up to 108GPa. Over the investigated pressure range the aggregate compressional sound velocity is ∼9% higher than in pure iron at the same density. The measured aggregate compressional (VP) and shear (VS) sound velocities, extrapolated to core densities and corrected for anharmonic temperature effects, are compared with seismic profiles. Our results provide constraints on the silicon abundance in the core, suggesting a model that simultaneously matches the primary seismic observables, density, P-wave and S-wave velocities, for an inner core containing 4 to 5wt.% of Ni and 1 to 2wt.% of Si.

Hugoniot temperatures and melting of tantalum under shock compression determined by optical pyrometry

LiF single crystal was used as transparent window (anvil) to tamp the shock-induced free surface expansion of Ta specimen, and the Ta/LiF interface temperature was measured under shock compression using optical pyrometry technique. The shock temperatures and/or melting temperatures of Ta up to ∼400 GPa were extracted from the observed interface temperatures based on the Tan–Ahrens’ model for one-dimensional heat conduction across metal/window ideal interface in which initial melting and subsequent solidification were considered under shock loading. The obtained data within the experimental uncertainties are consistent with the results from high-pressure sound velocity measurements. The temperature of the partial melting on Ta Hugoniot is estimated to be ∼9700 K at 300 GPa, supported by available results from theoretical calculations.

Single-crystal elasticity of diaspore, AlOOH, to 12 GPa by Brillouin scattering

The high-pressure elasticity of diaspore (AlOOH) has been determined by Brillouin spectroscopy to 12 GPa in diamond anvil cells. Experiments were carried out using a 16:3:1 methanol–ethanol–water mixture as pressure medium, and ruby as pressure standard. Acoustic velocities were measured in three roughly orthogonal planes at ambient and eight elevated pressures. The nine individual elastic stiffness constants of the orthorhombic crystal were obtained by fitting the velocity data to Christoffel's equation. Aggregate elastic moduli and pressure derivatives were calculated from the C ij s by fits to Eulerian finite strain equations, yielding: K S 0 = 152 ( 1 ) GPa , G 0 = 117.2(5) GPa, ( ∂ K S / ∂ P ) T 0 = 3.7 ( 1 ) , ( ∂ G / ∂ P ) 0 = 1.5 ( 1 ) for the Voigt–Reuss–Hill average. All individual C ij s increase with pressure but C 23 and C 55 exhibit anomalously low pressure derivatives. From calculated linear compressibilities, the a-axis is the most compressible. The b-axis becomes the least compressible axis at high pressures. Over the examined pressure range, the azimuthal P-wave anisotropy decreased from 22% to 16%, while the azimuthal S-wave anisotropy increased from 15% to 21%. Both volume and axial compression curves calculated using our Brillouin results are in good agreement with the results from static compression studies. High-pressure sound velocities in diaspore exceed those of other hydrous minerals as well as many anhydrous phases relevant to Earth's upper mantle.

High‐pressure sound velocities and elasticity of aluminous MgSiO3 perovskite to 45 GPa: Implications for lateral heterogeneity in Earth's lower mantle

Brillouin scattering measurements on aluminous magnesium silicate perovskite, arguably the most abundant phase in Earth, have been performed to 45 GPa in a diamond anvil cell at room temperature, using methanol‐ethanol‐water and neon as pressure transmitting media. The experiments were performed on a polycrystalline sample of aluminous MgSiO3 perovskite containing 5.1 ± 0.2 wt.% Al2O3. The pressure derivatives of the adiabatic bulk (K0S) and shear (μ0S) moduli are 3.7 ± 0.3 and 1.7 ± 0.2, respectively. These measurements allow us to evaluate whether the observed lateral variations of seismic wave speeds in Earth's lower mantle are due at least in part to a chemical origin. Our results indicate that a difference in the aluminum content of silicate perovskite, reflecting a variation in overall chemistry, is a plausible candidate for such seismic heterogeneity.

Unusual Grüneisen and Bridgman parameters of low-density amorphous ice and their implications on pressure induced amorphization

The low-temperature limiting value of the Grüneisen parameter for low-frequency phonons and the density dependence of the thermal conductivity (Bridgman parameter) of low-density amorphous (LDA) ice, high-density amorphous (HDA) ice, hexagonal ice Ih, and cubic ice Ic were calculated from high-pressure sound velocity and thermal conductivity measurements, yielding negative values for all states except HDA ice. LDA ice is the first amorphous state to exhibit a negative Bridgman parameter, and negative Grüneisen parameters are relatively unusual. Since Ih, Ic, and LDA ice all transform to HDA upon pressurization at low temperatures and share the unusual feature of negative Grüneisen parameters, this seems to be a prerequisite for pressure induced amorphization. We estimate that the Grüneisen parameter increases at the ice Ih to XI transition, and may become positive in ice XI, which indicates that proton-ordered ice XI does not amorphize like ice Ih on pressurization.

Sound velocity variations and melting of vanadium under shockcompression

The sound velocities of vanadium at shock pressure ranging from 154to 250 GPa were determined using transparent-window optical analysertechniques. A discontinuity in sound velocities at about 225 GPa may mark thepartial melting under shock compression. The comparison between the measuredsound velocity data sets above ~225 GPa and calculated values yieldsγ0≈2.0 and the empirical expression γρ = γ0ρ0is basically tenable. Additionally, shock temperatures along the principalHugoniot of vanadium were also determined from interfacial radiationintensities according to Grover's ideal interface model. Thus the temperatureat this solid-liquid phase transition was constrained to be round about7800(±800) K on the basis of the measured Hugoniot temperatures, meltingtemperatures, and high-pressure sound velocity variations with pressure.

High-pressure sound velocity of perovskite-enstatite and the possible composition of the Earth’s lower mantle

The compressional sound velocity Vp for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of VP, (in km/s) on Hugoniot pressure (P, in GPa) can be described by InVp= 3.079-0.691 In(P) + 0.094(lnP)2. Vp satisfies Birch’s law:V p = 4.068 + 1.677ρ, where ρ is corresponding density, which indicated that enstatite is stable throughout the conditions of the lower mantle. The wave velocityP is 0.5% lower and the wave velocity S is 2% higher than that of PREM respectively. We concluded that the lower mantle is mainly composed of perovskite-(Mg1-x, Fex) SiO3 and only a small amount of (Mg1-x, Fex) O is allowed in it.

High-Pressure Sound Velocity of Perovskite-Enstatite and Possible Composition of Earth's Lower Mantle

The compressional sound velocity vp for enstitate of polycrystalline specimens was measured at pressures from 40 to 140 GPa by using the optical analyzer techniques under shock loading. The dependence of vp (in units of km/s) on Hugoniot pressure p (in units of GPa) can be described by: ln vp = 3.079 - 0.691 ln p + 0.094 ln2 p. The vp satisfies Birch's law: vp = 6.213 + 1.212ρ, where ρ is corresponding density, indicating that enstatite is stable throughout the conditions of the lower mantle. Here P wave velocity is 0.5% lower and S wave velocity is 2% higher than those of preliminary reference earth model, respectively. It is concluded that the lower mantle is mainly composed of perovskite-(Mg1-x,Fex)SiO3 and only small amount of (Mg1-x,Fex)O is allowed in it.