We report the P-V-T equation of state measurements
of B4C to 50GPa and approximately 2500K in
laser-heated diamond anvil cells. We obtain an
ambient temperature, third-order Birch–Murnaghan
fit to the P-V 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 temperature-dependent, Birch–
Murnaghan equation of state that includes thermal
pressure estimated by thermal expansion (α) and
a temperature-dependent 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 P-T range of this study.
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Experimental and theoretical P-V-T equation of state for Os 2 B 3
Thermoelastic behavior of transition metal boride Os2B3 was studied under quasi-hydrostatic and isothermal conditions in a Paris-Edinburgh cell to 5.4 GPa and 1273 K. In-situ Energy Dispersive X-ray diffraction was used to determine interplanar spacings of the hexagonal crystal structure and thus the volume and axial compression. P-V-T data were fitted to a 3rd Order Birch-Murnaghan 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 P-V curve. Under a quadratic fit α=α_0+α_1 T-α_2 T^(-2), the thermal expansion coefficients were determined to be α_0=1.862×10^(-5) K-1, α_1=0.841×10^(-9) K-2, and α_2=-0.525 K. Density functional theory (DFT) with the quasi-harmonic approximation (QHA) were further employed to study Os2B3, including its P-V-T curves, phonon spectra, bulk modulus, specific heat, thermal expansion, and the Grüneisen parameter. A good agreement between the first-principle theory and experimental observations was achieved, highlighting the success of the Armiento-Mattsson 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
- NSF-PAR ID:
- 10207502
- Date Published:
- Journal Name:
- High Pressure Research
- ISSN:
- 0895-7959
- Page Range / eLocation ID:
- 1 to 12
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1080/08957959.2020.1858821
