High-pressure dysprosium carbides containing carbon dimers, trimers, chains, and ribbons

Abstract

Exploring the chemistry of materials at high pressure leads to discoveries of previously unknown compounds and phenomena. Here chemical reactions between elemental dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures up to 95 GPa and temperatures of ∼2800 K. In situ single-crystal synchrotron X-ray diffraction (SCXRD) analysis of the reaction products revealed the formation of novel dysprosium carbides, γ-DyC₂, Dy₅C₉, and γ-Dy₄C₅, along with previously reported Dy₃C₂ and Dy₄C₃. The crystal structures of γ-DyC₂ and Dy₅C₉ feature infinite flat carbon polyacene-like ribbons and cis-polyacetylene-type chains, respectively. In the structure of γ-Dy₄C₅, carbon atoms form dimers and non-linear trimers. Dy₃C₂ contains ethanide-type carbon dumbbells, and Dy₄C₃ is methanide featuring single carbon atoms. Density functional theory calculations reproduce well the crystal structures of high-pressure dysprosium carbides and reveal conjugated π-electron systems in novel infinite carbon polyanions. This work demonstrates that complex carbon homoatomic species previously unknown in organic chemistry can be synthesized at high pressures by direct reactions of carbon with metals.