Origin of Pressure‐Induced Metallization in Cu3N: An X‐ray Absorption Spectroscopy Study. Issue 11 (25th June 2018) - Kuzmin, Alexei
Abstract : High‐pressure (0–26.7 GPa) Cu K‐edge X‐ray absorption spectroscopy is used to study possible structural modifications of anti‐perovskite‐type copper nitride (Cu3 N) crystal lattice. The analysis of X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS), based on theoretical full‐multiple‐scattering and single‐scattering approaches, respectively, suggests that at all pressures the local atomic structure of Cu3 N remains close to that in cubic P m 3 ¯ m phase. Therefore, the transition to metal state above 5 GPa, observed previously using pressure‐dependent electrical resistance and optical absorption measurements, is explained by the band gap collapse due to a decrease of the unit cell volume. We found that the lattice parameter of Cu3 N is reduced by ≈2% upon increasing pressure up to 26.7 GPa, and the structure is restored upon pressure release. Abstract : Origin of pressure‐induced metallization in cubic Cu3 N has been disclosed using in situ Cu K‐edge X‐ray absorption spectroscopy. The transition to metal state above 5 GPa is explained by the band gap collapse due to a decrease of the unit cell volume. The lattice parameter of Cu3 N is reduced by ≈2% upon increasing pressure up to 26.7 GPa, and the structure is restored upon pressure release. The local atomic structure of Cu3 N remains close to that in cubic P m 3 ¯ m at all pressures.