Dr. Elissaios Stavrou
Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Material Science
Division, Livermore, California 94550, USA
Novel synthesis pathways have become critically important in the development of materials that are precisely tailored to meet the need for specific properties/applications, i.e. “materials by design.” One way to overcome present barriers in the synthesis of materials is to alter the fundamental chemistry that governs the relevant chemical systems. In this context, tuning the composition of a given chemical system beyond the
thermodynamically stable one at ambient conditions represents an extremely promising but poorly explored approach to the synthesis of novel materials. Recent theoretical predictions highlight that the chemical properties of elements, and thus the more stable stoichiometries of a chemical system, are not a priori the same at elevated pressures as at ambient pressure. Thus, pressure has the potential to become a game-changing approach for the synthesis of novel materials.
Indeed, thermodynamically stable compounds with novel compositions that challenge our traditional “textbook” picture were experimentally synthesized even in relatively simple chemical systems [1-7]. These materials can be synthesized due to the formation of chemical bonds and atomic arrangements that are absent, or even forbidden, at ambient conditions. Thus, by varying the stoichiometry one can design novel materials with enhanced properties, such as high energy density, hardness, high Tc superconductivity and materials for specific applications, such as anode materials. One of the great challenges is to devise such materials that will be metastable upon pressure release. Moreover, current outstanding questions, in geo- and planetary science could be addressed based on the stability of surprising stoichiometries that challenge our chemical intuition.
In this talk, I will present recent results and highlight the need of close synergy between experimental and theoretical efforts to understand the novel chemical properties of elements under high-pressure conditions in the challenging and complex field of variable stoichiometry under pressure. Finally, possible new routes for the synthesis of novel materials will be discussed.
- Adeleke et al., “High-pressure compound of argon and nickel: noble gas in the Earth’s core?”, ACS Earth Space Chem. 11, 2517 (2019)
- E. Stavrou et al., “Synthesis of Xenon and Iron-Nickel Intermetallic Compounds at Earth’s Core Thermodynamic Conditions”, Phys. Rev. Lett. 120, 096001 (2018)
- E. Stavrou et al., “Synthesis of ultra-incompressible sp3-hybridized carbon nitride”, Chem. Mater. 28, 6925 (2016)
- Steele et al. “High-Pressure Synthesis of a Pentazolate Salt”, Chem. Mater. 29, 735 (2017).
- X. Dong et al., “Stable Compound of Helium and Sodium at High Pressure”, Nat. Chem. 9, 440 (2017).
- Struzhkin et al., “Synthesis of Sodium Polyhydrides at High Pressures”, Nat. Commun. 7, 12267 (2016).
- W. Zhang et al., “Unexpected stable stoichiometries of sodium chlorides”, Science 342, 1502 (2013).