We report the PVT equation of state measurements
of B4C to 50GPa and approximately 2500K in
laserheated diamond anvil cells. We obtain an
ambient temperature, thirdorder Birch–Murnaghan
fit to the PV data that yields a bulk modulus K0
of 221(2) GPa and derivative, (dK/dP)0 of 3.3(1).
These were used in fits with both a Mie–Grüneisen–
Debye model and a temperaturedependent, Birch–
Murnaghan equation of state that includes thermal
pressure estimated by thermal expansion (α) and
a temperaturedependent bulk modulus (dK0/dT).
The ambient pressure thermal expansion coefficient
(α0+α1T), Grüneisen γ (V)=γ 0(V/V0)q and volumedependent
Debye temperature, were used as input
parameters for these fits and found to be sufficient to
describe the data in the whole PT range of this study.
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Experimental and theoretical PVT equation of state for Os 2 B 3
Thermoelastic behavior of transition metal boride Os2B3 was studied under quasihydrostatic and isothermal conditions in a ParisEdinburgh cell to 5.4 GPa and 1273 K. Insitu Energy Dispersive Xray diffraction was used to determine interplanar spacings of the hexagonal crystal structure and thus the volume and axial compression. PVT data were fitted to a 3rd Order BirchMurnaghan equation of state with a temperature modification to determine thermal elastic constants. The bulk modulus was shown to be K0 = 402 ± 21 GPa when the first pressure derivative was held to K0’ = 4.0 from the room temperature PV curve. Under a quadratic fit α=α_0+α_1 Tα_2 T^(2), the thermal expansion coefficients were determined to be α_0=1.862×10^(5) K1, α_1=0.841×10^(9) K2, and α_2=0.525 K. Density functional theory (DFT) with the quasiharmonic approximation (QHA) were further employed to study Os2B3, including its PVT curves, phonon spectra, bulk modulus, specific heat, thermal expansion, and the Grüneisen parameter. A good agreement between the firstprinciple theory and experimental observations was achieved, highlighting the success of the ArmientoMattsson 2005 generalized gradient approximation functional employed in this study and QHA for describing thermodynamic properties of Os2B3.
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 Award ID(s):
 1904164
 NSFPAR ID:
 10207502
 Date Published:
 Journal Name:
 High Pressure Research
 ISSN:
 08957959
 Page Range / eLocation ID:
 1 to 12
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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