Pressure-induced hydrogen transfer and polymerization in crystalline furoxan

Abstract

The structural transformations, electronic structure, elastic constants, and absorption properties of crystalline furoxan under hydrostatic compression of 0–160 GPa have been studied using density functional theory. The results show that furoxan (S1) undergoes a hydrogen transfer to form a new structure (named S2) with a planar conformation approximately at 114–115 GPa. Then, it goes through another hydrogen transfer to form a second new structure (named S3) with chair conformation at 124 GPa. Finally, it undergoes polymerization to form another new structure (named S4) with a trans-conformation at 136 GPa. An analysis of its band gaps and density of states under compression indicates that it changes from an insulator to a semiconductor in the pressure range 0–113 GPa. S2 and S4 have metallic properties, while S3 is an insulator. The calculated elastic constants show that the three new structures are mechanically stable. Its absorption spectra show that S2 has higher optical activity than S1. S3 has higher optical activity than S2 in the far ultraviolet region, while S4 has weaker optical activity than S3 in this region. S4 and S2 have comparative optical activity.