Carbon exists in the solid state in many forms over a wide range of thermodynamical conditions. While important resources have been dedicated to its study at ambient conditions, much remains uncertain about the behavior of carbon and carbon-based solids at extreme conditions (EC) of pressure and temperature. This includes bonding environments, structure and crystal chemistry, stability ranges, reaction rates, and relative abundance.
Recently interest in the study of carbon under EC has been thoroughly revived. The carbon-based chemistry is just as fascinating at high pressures as at ambient conditions:
- a new compound was synthesized by reacting CO2 and SiO2 in a laser heated diamond anvil cell at pressures between 16 GPa and 22 GPa, and temperatures in excess of 4000 K, showing that carbon enters silica. These findings are of paramount relevance for an updated view of the periodic table of elements and for planetary sciences (Santoro et al., 2014).
- amorphous silicon oxycarbide polymer-derived ceramics (PDCs), synthesized from organometallic precursors, contain carbon- and silica-rich nanodomains, the latter with extensive substitution of carbon for oxygen, linking Si-centered SiOxC4-x tetrahedra (Sen et al., 2013).
- under various deep planetary conditions methane reacts, and as pressure and temperature increase the chemical signature of the hydrocarbon fluid changes. The authors observed production of heavy hydrocarbons under deep mantle conditions, and also detected elemental carbon precipitation (Lobanov et al., 2013).
Developments in geophysics and carbon geochemistry are just as captivating:
- Wu and Buseck, instead, envisage crystallographic defects in mantle minerals as an alternative carbon sink, broadening the inference that grain boundaries of mantle minerals could be localized sites for carbon enrichment [Dasgupta and Hirschmann, 2010; Wu and Buseck, 2013]
- the isotopic fractionation of carbon can occur in the mantle at minimum temperatures and pressures, consistent with the top of the diamond stability field when iron carbides are involved (Mikhail et al., 2014). Co-genesis of carbide and diamond can therefore produce abiogenic reservoirs of 13C-depleted carbon that overlap isotopically “light” carbon conventionally attributed to subducted organic carbon.
This general effort is reflected in a series of individual initiatives, special sessions at international conferences, dedicated workshops and schools, etc. The constitution of the Deep Carbon Observatory Consortium (https://deepcarbon.net/), plays an important role in leveraging the knowledge and skills of a global, interdisciplinary community for transforming our knowledge of carbon.
We are in the middle of a revival of the study of carbon in its various forms over the widest imaginable thermodynamic conditions. Our workshop follows this great momentum for research and aims to bring together scientists with broad interests, physicists, chemists, mineralogists, planetary scientists, who share a common interest in carbon.