Structural Studies on Metallization of Solid Oxygen

点击翻译按钮获取中文摘要

1.By using high-energy and high-brilliance synchrotron radiation source in ESRF and PF,an energy-dispersive powder X-ray diffraction study on solid oxygen has been carried out up to 181 GPa at room temperature. A new high-pressure structural transition was observed at 96 GPa. The phase transition to zeta-O_2 is ascribed to metallization previously reported by S.Desgreniers et al. The metallic phase was stable up to 181 GPa.2.High-pressure Raman spectroscopy of solid oxygen has been carried out up to 110 GPa at room temperature in order to study the structural transition to the metallic phase at 96 GPa. The vibron and librons in the epsilon-O_2 phase became undetectable corresponding to the structural transition to metallic phase, although the vibron wavenumber in the epsilon-O_2 phase has shown a linear pressure dependence with a coefficient of 2.33 cm^<-1>/GPa and reached 1753 cm^<-1> at 94 GPa.3.Single-crystal of the epsilon-O_2 phase, which exhibited a remarkable dichromatic character, were prepared by a strain anneal method under a condition of 25 GPa and 650 K and were used for infrared absorption experiments under pressure up to 60 GPa. The IR-active vibron fundamental around 1500 cm^<-1> split into at least three bands. The pressure dependence of frequency of the IR-vibrons had a minimun around 25 GPa and above 30 GPa showed positive pressure coefficients between 1.2-1.7 cm^<-1>/GPa.Thes results suggested that the metallic zeta-O_2 phase consisted of O_2 molecules.