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High pressure study on ultra-hard transition-metal boride Os2B3 was carried out in a diamond anvil cell under isothermal and non-hydrostatic compression with platinum as an X-ray pressure standard. The ambient-pressure hexagonal phase of Os2B3 is found to be stable with a volume compression V/V0 = 0.670 ± 0.009 at the maximum pressure of 358 ± 7 GPa. Anisotropic compression behavior is observed in Os2B3 to the highest pressure, with the c-axis being the least compressible. The measured equation of state using the 3rd-order Birch-Murnaghan fit reveals a bulk modulus K0= 397 GPa and its first pressure derivative K0'= 4.0. The experimental lattice parameters and bulk modulus at ambient conditions also agree well with our density-functional-theory (DFT) calculations within an error margin of ~1%. DFT results indicate that Os2B3 becomes more ductile under compression, with a strong anisotropy in the axial bulk modulus persisting to the highest pressure. DFT further enables the studies of charge distribution and electronic structure at high pressure. The pressure-enhanced electron density and repulsion along the Os and B bonds result in a high incompressibility along the crystal c-axis. Our work helps to elucidate the fundamental properties of Os2B3 under ultrahigh pressure for potential applications in extreme environments.
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Development of a machine learning interatomic potential for exploring pressure-dependent kinetics of phase transitions in germanium
We introduce a data-driven potential aimed at the investigation of pressure-dependent phase transitions in bulk germanium, including the estimate of kinetic barriers. This is achieved by suitably building a database including several configurations along minimum energy paths, as computed using the solid-state nudged elastic band method. After training the model based on density functional theory (DFT)-computed energies, forces, and stresses, we provide validation and rigorously test the potential on unexplored paths. The resulting agreement with the DFT calculations is remarkable in a wide range of pressures. The potential is exploited in large-scale isothermal-isobaric simulations, displaying local nucleation in the R8 to β-Sn pressure-induced phase transformation, taken here as an illustrative example.
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- Award ID(s):
- 2102317
- PAR ID:
- 10566100
- Publisher / Repository:
- American Physical Society
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 161
- Issue:
- 1
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0214588
