Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray driven first-order phase transition in GeO2 glass under pressure   Unprecedented bright and intense synchrotron X-rays have been widely used to
unravel numerous compelling electronic and structural properties using a large
variety of physical techniques, while the puzzling phenomenon is the
uncertainties of measurements due to X-ray induced considerable electronic and
structural changes of a matter under study. Here, we report an X-ray driven
first-order tetrahedral-octahedral phase transition in GeO2 glass at high
pressure using X-ray absorption fine structure (XAFS) with a
nano-polycrystalline diamond anvil (NPD) cell. Upon X-ray irradiation from an
undulator device, the XAFS spectrum at 5.4 GPa, which is below the threshold
pressure of tetrahedral to pentahedral transition, starts to progressively
approach the spectrum of octahedral GeO2 at 20.4 GPa. Detailed analysis
indicates that both the nearest distance and coordination number of GeO2 glass
at 5.4 GPa increase to those of a fully octahedral glass above 20 GPa, while
negligible changes were found at other low pressures. These observations
demonstrate that X-ray irradiation can be served as an alternative stimulus for
forming dense matter under pressure, as the well-known external stimuli of
pressure and temperature. Dense matter formed under external stimuli is crucial
for understanding the formation, differentiation and evolution of planet and
Earth. Attention for the X-ray induced structural uncertainties is called,
especially for addressing metastable states under extreme conditions which may
become undetectable in terms of intense synchrotron X-rays as structural tools.

25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys