Research

Pressure is a powerful tool for tuning the properties of matter. In the lab, we can easily subject our (very small) samples to pressures in the range of a kilobar to a megabar (1 000 to 1 000 000 times atmospheric pressure).

I investigate the exotic behavior of matter under extreme conditions, mostly small light molecules under high pressure. Understanding how materials respond at the microscopic level provides fundamental insights that can guide the design of advanced materials for future technological applications.

Here’s what I’ve been obsessing over lately:

• Polymorphism in nitrogen and simple nitrogen-rich systems
  (Laniel et al. Nature Comm. 2023; Koller et al. Angew. Chem. Int. Ed. 2024)

• Synthesis and structural characterization of new compounds
  (Ranieri et al. Phys. Rev. Lett. 2022; Ranieri et al. Phys. Rev. Materials 2026)

• Reactivity and emergence of new chemical species
  (Aslandukov et al. JACS 2024; Ranieri et al. JACS 2025; Spender et al. JACS 2026)

• Dynamical disorder in crystalline solids
  (Ranieri et al. Nature Comm. 2017; Rescigno et al. J. Phys. Chem. B 2023)

• Plastic water ice
  (Toffano et al. J. Chem. Phys. 2022; Rescigno et al. Nature 2025)

• Structural phase transitions in gas clathrate hydrates
  (Schaack et al. PNAS 2019; Ranieri et al. PNAS 2023; Frost et al. Comm. Chemistry 2025)

• Hard, ultra-incompressible materials
  (Liang et al. Adv. Funct. Mater. 2024; Laniel et al. Adv. Funct. Mater. 2025; Liang et al. Phys. Rev. B 2026)

• Molecular diffusion in compressed fluids
  (Ranieri et al. J. Phys. Chem. B 2016; Ranieri et al. Nature Comm. 2021; Ranieri et al. Nature Comm. 2024)

• Quantum transitions of H₂ confined within nanocages
  (Ranieri et al. J. Phys. Chem. C 2019; Ranieri et al. J. Chem. Phys. 2024; Di Cataldo et al. Phys. Rev. Lett. 2024)

• Hydrogen-bond symmetrization
  (Schaack et al. J. Phys. Chem. C 2018; Monacelli et al. Phys. Rev. B 2025)

A large part of my research is directly relevant for energy-related applications. Some of it is relevant for planetary science (Bove and Ranieri Phil. Trans. R. Soc. A 2019).

I am frequently using large-scale facilities for my experiments, including synchrotrons and neutron sources. I am very interested in developing new methodologies for pushing the boundaries of experimental techniques.