Geometries and stabilities of chromium doped nitrogen clusters: mass spectrometry and density functional theory studies

Abstract

Metal-doped nitrogen clusters serve as effective models for elucidating the geometries and electronic properties of nitrogen-rich compounds at the molecular scale. Herein, we have conducted a systematic study of VIB-group metal chromium (Cr) doped nitrogen clusters through a combination of mass spectrometry techniques and density functional theory (DFT) calculations. The laser ablation is employed to generate CrN_n⁺ clusters. The results reveal that CrN₈⁺ cluster exhibits the highest signal intensity in mass spectrometry. The photodissociation experiments with 266 nm photons confirm that the chromium heteroazide clusters are composed of chromium ions and N₂ molecules. Further structural searches and electronic structure calculations indicate that the cationic CrN₈⁺ cluster possesses an X shaped geometry with D₂ symmetry and exhibits robust stability. Molecular orbital and chemical bonding analyses demonstrate the existence of strong interactions between Cr⁺ cation and N₂ ligands. The present findings enrich the geometries of metal doped nitrogen clusters and provide valuable guidance for the rational design and synthesis of novel transition metal nitrides.