Exploring the chemistry of materials at high pressures enables the discovery of previously unknown, but frequently exotic, compounds. We systematically searched for all thermodynamically stable Sr-C compounds under pressure (up to 100 GPa) using the ab initio evolutionary crystal structure prediction method. Our search led to the discovery of hitherto unknown phases of ${\mathrm{SrC}}_3, {\mathrm{Sr}}_2{\mathrm{C}}_5, {\mathrm{Sr}}_2{\mathrm{C}}_3, {\mathrm{Sr}}_2\mathrm{C}, {\mathrm{Sr}}_3{\mathrm{C}}_2$, and SrC. The discovered crystal structures feature a variety of different carbon environments ranging from isolated C anions and C dimers to exotic polyatomic carbon anions, including chains, stripes, and infinite ribbons consisting of pentagonal ${\mathrm{C}}_5$ and hexagonal ${\mathrm{C}}_6$ rings. The dynamical stability of all predicted compounds is confirmed by phonon calculations. Bader analysis unravels very diverse chemistry in these compounds, and bonding patterns in some of them can be described using the Zintl-Klemm rule.

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• Crystal structure
• High-pressure studies
• Structural properties
• Carbides
• Density functional calculations
• High-throughput calculations