Graphdiyne under pressure: A Raman study

High pressure Raman spectra of graphdiyne (GDY) have been studied up to 34.63 GPa. We found that sp-hybridized carbons in GDY are highly active and start to undergo a bonding change at around 5.2 GPa. Such a bonding change affects the C-C stretching vibration of sp2 hexagon rings in GDY, leading to an anomaly in the corresponding G-band pressure coefficient. A three-dimensional sp2 structure is proposed to form via pressure-induced interlayer cross-linking of sp carbons in GDY and is stable up to at least 34.63 GPa. Our study presents an important example in the study of graphyne family under pressure.