Hiroki Kobayashi
I am working as...
- Chercheur invité (Guest Researcher) at Institut de minéralogie, de physique des matériaux et de cosmochimie, Sorbonne University, France. Working with Stefan Klotz.
- PhD student at Geochemical Research Centre, Graduate School of Science, the University of Tokyo, Japan. Working with Kazuki Komatsu and Hiroyuki Kagi.
Research Interest
High-pressure, water, ice, aqueous solutions, phase transition, crystallography, experimental mineral physics and chemistry
Software Skills: Click here to Show
Languages
English (upper intermediate) & Japanese (native)
Research History
- Feb. 2025 – current. Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université. Chercheur invité (Invited Researcher).
- Apr. 2021 – current. Geochemical Research Center, Graduate School of Science, The University of Tokyo.
Recent news
- I am staying at IMPMC, Sorbonne Univ., Paris, from Feb. 2025 as an invited researcher hosted by Dr Stefan Klotz.
- I discovered three new phases of ice and their structure arXiv preprint
- We reported weak hydrogen ordering in ice IV H.K. et al., JPCL (2023)
Featured Works
Densification processes of crystalline purine: Negative linear compressibility and pressure-induced phase transition
, Kazuki Komatsu, and Hiroyuki Kagi.
Chemical Physics Letters (2025)
DOI: 10.1016/j.cplett.2025.142600
Slightly Hydrogen-Ordered State of Ice IV Evidenced by In-Situ Neutron Diffraction
, Kazuki Komatsu, Hayate Ito, Shinichi Machida, Takanori Hattori, and Hiroyuki Kagi.
The Journal of Physical Chemistry Letters (2023) 14 10664
DOI: 10.1021/acs.jpclett.3c02563
We reported crystallographic evidence for the hydrogen ordering in ice IV by neutron diffraction. It shows discontinuous behaviour at 120 K and Rietveld analysis at the low-T side suggests it is a very weak hydrogen ordering structural transition.
Awards
- Aug. 2025: IUCr Young Scientist Award (for the attendance at ECM35)
- Feb. 2025: Ludo Frevel Crystallography Scholarship Award from International Centre for Diffraction Data (ICDD). "In-depth neutron diffraction study of unusual hydrogen ordering behaviour in ice VI" (2,500 USD)
- Mar. 2024: Graduate School of Science Awards (for MSc studies), UTokyo
- Aug. 2023: CrSJ Travel Award (for the attendance at IUCr2023)
- Mar. 2022: Department of Chemistry Chair Award (for BSc studies), Faculty of Science, UTokyo
Grants
- 04/2026 – 03/2028. Research Fellowships for Young Scientists from Japan Society of Promotion of Science (JSPS). "Structural diversity of salty ice: generalised understanding focusing on density, crystal structure, and ionic species"
- 02/2025 – 02/2026. Overseas Challenge Program for Young Researchers (1,400,000 JPY + transportation costs) from Japan Society of Promotion of Science (JSPS). "Precise analysis of the hydrogen-atom distribution in a high-pressure phase of ice by single-crystal neutron diffraction"
- 04/2024 – 02/2025. Sasakawa Scientific Research Grant from The Japan Science Society (880,000 JPY)
We studied pressure-induced structural changes in crystalline purine (C5H4N4). The ambient phase persists up to about 0.7 GPa until it transforms into a newly characterised high-pressure phase with a completely different packing structure. We pointed out that the intermolecular hydrogen bonds may be doubled, for which further spectroscopic/theoretical corroboration is desired. If so, we suggest this phase transition is characteristic in purine but not expected in pyrimidine, which has no ability to double the hydrogen bonds.