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Unprecedented bright and intense synchrotron X-rays have been widely used tounravel numerous compelling electronic and structural properties using a largevariety of physical techniques, while the puzzling phenomenon is theuncertainties of measurements due to X-ray induced considerable electronic andstructural changes of a matter under study. Here, we report an X-ray drivenfirst-order tetrahedral-octahedral phase transition in GeO2 glass at highpressure using X-ray absorption fine structure (XAFS) with anano-polycrystalline diamond anvil (NPD) cell. Upon X-ray irradiation from anundulator device, the XAFS spectrum at 5.4 GPa, which is below the thresholdpressure of tetrahedral to pentahedral transition, starts to progressivelyapproach the spectrum of octahedral GeO2 at 20.4 GPa. Detailed analysisindicates that both the nearest distance and coordination number of GeO2 glassat 5.4 GPa increase to those of a fully octahedral glass above 20 GPa, whilenegligible changes were found at other low pressures. These observationsdemonstrate that X-ray irradiation can be served as an alternative stimulus forforming dense matter under pressure, as the well-known external stimuli ofpressure and temperature. Dense matter formed under external stimuli is crucialfor understanding the formation, differentiation and evolution of planet andEarth. Attention for the X-ray induced structural uncertainties is called,especially for addressing metastable states under extreme conditions which maybecome undetectable in terms of intense synchrotron X-rays as structural tools.

X-ray driven first-order phase transition in GeO2 glass under pressure