1,137 research outputs found
Effective Volumetric Factor for Inhomogeneous Temperature in Volumetric Measurements of Gas Absorption and Desorption
Accounting of effective volumetric factor for the measurement at
inhomogeneous temperature allows to the simplify the measurement process
avoiding a pre-calibration with a noble gas. The volumetric correction in form
of the volumetric factor is calculated analytically by modeling of the
temperature profile in the volumetric apparatus, and provides a quite agreement
with the measured results. The calculation can be applied for each volumetric
measurement with an inhomogeneous temperature distribution
Semimetallic molecular hydrogen at pressure above 350 GPa
According to the theoretical predictions, insulating molecular hydrogen
dissociates and transforms to an atomic metal at pressures P~370-500 GPa. In
another scenario, the metallization first occurs in the 250-500 GPa pressure
range in molecular hydrogen through overlapping of electronic bands. The
calculations are not accurate enough to predict which option is realized. Here
we show that at a pressure of ~360 GPa and temperatures <200 K the hydrogen
starts to conduct, and that temperature dependence of the electrical
conductivity is typical of a semimetal. The conductivity, measured up to 440
GPa, increases strongly with pressure. Raman spectra, measured up to 480 GPa,
indicate that hydrogen remains a molecular solid at pressures up to 440 GPa,
while at higher pressures the Raman signal vanishes, likely indicating further
transformation to a good molecular metal or to an atomic state
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