The compressional (P) and shear wave velocities (S) and unit cell volumes (densities) of polycrystalline tungsten (W) have been measured simultaneously up to 10.5 GPa and 1073 K using ultrasonic interferometry in conjunction with x-ray diffraction and x-radiography techniques. Thermoelastic properties of W were derived using different methods. We obtained the isothermal bulk modulus KT0 = 310.3(1.5) GPa, its pressure derivative K′T0 = 4.4(3), its temperature derivative at constant pressure (∂KT/∂T)P=−0.0138(1)GPaK−1 and at constant volume (∂KT/∂T)V=−0.0050GPaK−1, the thermal expansion α(0, T) = 1.02(27) × 10−5 + 7.39(3.2) × 10−9 T (K−1), as well as the pressure derivative of thermal expansion (∂α/∂P)T=−1.44(1)×10−7K−1GPa−1 based on the high-temperature Birch–Murnaghan equation of state (EOS), the Vinet EOS, and thermal pressure approach. Finite strain analysis allowed us to derive the elastic properties and their pressure/temperature derivatives independent of the choice of pressure scale. A least-squares fitting yielded KS0 = 314.5(2.5) GPa, KS0′ = 4.45(9), (∂KS/∂T)P = − 0.0076(6) GPa K−1, G0 = 162.4(9) GPa, G0′ = 1.8(1), (∂G/∂T)P = − 0.0175(9) GPa K−1, and α298K=1.23×10−5K−1. Fitting current data to the Mie–Grüneisen–Debye EOS with derived θ0=383.4K yielded γ0=1.81(6)andq=0.3. The thermoelastic parameters obtained from various approaches are consistent with one another and comparable with previous results within uncertainties. Our current study provides a complete and self-consistent dataset for the thermoelastic properties of tungsten at high P–T conditions, which is important to improve the theoretical modeling of these materials under dynamic conditions.

The thermal conductivity (κ $\kappa $) and thermal diffusivity (D $D$) of talc have been measured over a range of temperature (298–1,373 K) and pressure (0.5–3.0 GPa) conditions using the transient plane‐source method. The results show that both the thermal conductivity and thermal diffusivity are dependent upon the prevailing temperature and pressure conditions to a certain extent. As the temperature and pressure increase, the thermal diffusivity monotonically decreases, while the thermal conductivity initially decreases between 298 and 973 K and then increases from 973 to 1,173 K. At low temperatures, phonon scattering is the dominant mechanism for heat transfer; at higher temperatures, photon radiation and dehydration become more prevalent. At temperatures greater than 1,173 K, the thermal conductivity decreases significantly due to aqueous liquid accumulation. Talc may be the cause of the high geothermal gradient in the hot subduction zone.

We measured the elastic velocities of a synthetic polycrystalline β-Mg2SiO4 containing 0.73 wt.% H2O to 10 GPa and 600 K using ultrasonic interferometry combined with synchrotron X-radiation. Third-order Eulerian finite strain analysis of the high P and T data set yielded Kso = 161.5(2) GPa, Go = 101.6(1) GPa, and (∂Ks/∂P)T = 4.84(4), (∂G/∂P)T = 1.68(2) indistinguishable from Kso = 161.1(3) GPa, Go = 101.4(1) GPa, and (∂Ks/∂P)T = 4.93(4), (∂G/∂P)T = 1.73(2) from the linear fit. The hydration of the wadsleyite by 0.73 wt.% decreases Ks and G moduli by 5.3% and 8.6%, respectively, but no measurable effect was noted for (∂Ks/∂P)T and (∂G/∂P)T. The temperature derivatives of the Ks and G moduli from the finite strain analysis (∂KS/∂T)P = −0.013(2) GPaK−1, (∂G/∂T)P = −0.015(0.4) GPaK−1, and the linear fit (∂KS/∂T)P = −0.015(1) GPaK−1, (∂G/∂T)P = −0.016(1) GPaK−1 are in agreement, and both data sets indicating the |(∂G/∂T)P| to be greater than |(∂KS/∂T)P|. Calculations yield ∆Vp(α-β) = 9.88% and ∆VS(α-β) = 8.70% for the hydrous β-Mg2SiO4 and hydrous α-Mg2SiO4, implying 46–52% olivine volume content in the Earth’s mantle to satisfy the seismic velocity contrast ∆Vs = ∆VP = 4.6% at the 410 km depth.

Compressional (VP) and shear wave (VS) velocities of polycrystalline tungsten have been measured up to ∼13 GPa at room temperature using ultrasonic interferometry in a multi-anvil apparatus. Using finite strain equation of state approaches, the elastic bulk and shear moduli and their pressure dependences are derived yielding KS0=325.9±4.8  GPa,  G0=164.1±2.5  GPa, KS0′=3.65±0.05, and G0′=1.28±0.02. On the basis of the current experimental data, the high-pressure behavior of Young's modulus, Poisson's ratio, and ductility/brittleness for tungsten are also investigated. Complementary to the experimental data, the single crystal elastic constants, as well as the elastic anisotropy of tungsten are computed using density functional theory (DFT). The Voigt-Reuss-Hill average of the bulk and shear moduli calculated using the single crystal elastic constants from DFT are found comparable to the current experimental results within about 5%. The present study offers a dataset for the elasticity of polycrystalline bcc tungsten to a maximum pressure more than 25-fold higher than other previous ultrasonic studies, which can further our understanding about the elastic, mechanical, and electronic properties of tungsten under extreme conditions as well as thermodynamic modelling of its alloys.

Synthetic olivine-antigorite aggregates serve as proxies for mantle wedge lithologies • We empirically explore the relationship between the acoustic velocity and the degree of serpentinization and pressure • The degree of serpentinization and the water content of the mantle wedges of 19 typical subduction zones are determined