P–V–T equation of state of rhodium oxyhydroxide

ABSTRACT

A high pressure X-ray diffraction study of RhOOH was carried out up to 17.44 GPa to investigate the compression behavior of an oxyhydroxide with an InOOH-related structure. A fit to the third-order Birch–Murnaghan equation of state gave K₀ = 208 ± 6 GPa, and K′ = 9.4 ± 1.3. The temperature derivative of the bulk modulus was found to be ∂K/∂T = −0.06 ± 0.02 GPa K⁻¹. The refined parameters for volume thermal expansion were α₀ = 2.7 ± 0.3 × 10⁻⁵ K⁻¹; α₁ = 1.7 ± 1.1 × 10⁻⁸ K⁻² in the polynomial form (α(T) = α₀+ α₁(T−300)). Our results show that RhOOH is very incompressible, and has a higher bulk modulus than other InOOH-structured oxyhydroxides (e.g. δ-AlOOH, ε-FeOOH, and γ-MnOOH).

KEYWORDS:

• RhOOH
• InOOH-type oxyhydroxide
• equation of state

Acknowledgements

We thank Y. Horioka, N. Hisano, and K. Obata for their technical support.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by KAKENHI: [grant numbers JP21684032, JP20103003, JP15H05826, JP15H05828, and JP16K13901] from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The synchrotron X-ray experiments were performed at the Photon Factory, High Energy Accelerator Research Organization KEK [Proposal nos. 2006G044, 2010G182, and 2015G524].