Electronic structure and anisotropic compression of Os2B3to 358 GPa
Kaleb C Burrage1, Chia-Min Lin1, Wei-Chih Chen1
1Department of Physics, University of Alabama at Birmingham, Birmingham, AL, 35294, United States of America.
Abstract:
High pressure study on ultra-hard transition-metal boride Os2B3was 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 Os2B3is found to be stable with a volume compressionV/V0= 0.670 ± 0.009 at the maximum pressure of 358 ± 7 GPa. Anisotropic compression behavior is observed in Os2B3to the highest pressure, with thec-axis being the least compressible. The measured equation of state using the 3rd-order Birch-Murnaghan fit reveals a bulk modulusK0=397 GPa and its first pressure derivativeK0'=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 Os2B3becomes 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 crystalc-axis. Our work helps to elucidate the fundamental properties of Os2B3under ultrahigh pressure for potential applications in extreme environments.
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