Structural environment of krypton dissolved in vitreous silica

Interstitial voids in silica melts and implication for argon solubility under high pressures

“…This is confirmed by X-ray absorption measurements in silica that the krypton atoms take the site of void surrounded by nearest oxygen atoms (Wulf et al, 1999). The solubilities of noble gases in silicate melts under lower pressures are reported to be roughly correlated with the properties of melts such as density (Lux, 1987), ionic porosity (Carroll and Stolper, 1993;Marrocchi and Toplis, 2005) or the number of non-bridged oxygen per silicon (NBO/Si) (Shibata et al, 1998), but the relevancies between the experimental solubility and these prosperities are still controversial since the results from different composition are inconsistent (Marrocchi and Toplis, 2005;Shibata et al, 1998).…”

“…We notice that the radius of O is $3 times larger than Si, which means the volume occupied by O is $100 times than Si. In addition, both simulation (Zhang et al, 2009) and experiment (Wulf et al, 1999) show that the nearest neighbors for atoms of solute in silica melts are always O atoms, whereas Si occupies the center of tetrahedron (it will be checked later). Hence we calculated interstitial voids only from the sublattice of O and removed the ones occupied by Si as also suggested by Chan and Elliott (1991).…”

X-ray fluorescence and absorption analysis of krypton in irradiated nuclear fuel

“…The backscattering amplitude functions for oxygen and noble gases are different. For oxygen as a neighbour, the oscillations are damped more rapidly than for the xenon or krypton even if the interpretation may be some what different from the study on the effect of oxygen surrounding environment of krypton dissolved in vitreous silica, [22]. The absence of rapid decrease of the XAFS signal (Fig.…”

The effect of compression on noble gas solubility in silicate melts and consequences for degassing at mid-ocean ridges

“…This finding can be rationalized in pointing out that the total polarizing field F acting on the solute is the result of a summation over all the individual fields emanating from the ionic species forming the silicate. In pure silica melt, it has been established both by simulation (Guillot and Guissani, 1996a) and by X-ray scattering (Wulf et al, 1999) that the noble gases occupy, in the silica network, the center of a cage (clathrate-like) of rather high symmetry and hence the Coulomb field felt by the rare gas atom is cancelled to a large extent, the net result being a weak polarization energy. This explains why the noble gases, in a highly silicic melt as rhyolite, exhibit a much smaller polarization energy than in a less polymerized melt like a MORB.…”