Diffusion of hydrogen in (Mg,Fe)2SiO4 and high pressure polymorphs refined by the cBΩ model

Modeling H, Na, and K diffusion in plagioclase feldspar by relating point defect parameters to bulk properties

“…No theoretical or experimental corresponding values of activation volume are available in the literature. However, our calculated υ act (5.39-5.41 cm 3 / mol) based on the cBΩ model of hydrogen diffusion in plagioclase feldspar is comparable with those of hydrogen diffusion in forsterite (4.02-8.50 cm 3 /mol, depending on direction) reported by Zhang (2012). Nevertheless, calculated values of υ act for Na and K diffusion in albite are at least three times larger than those (1.45 cm 3 /mol) derived from electrical conductivity measurements in alkali feldspar when Na + or K + ions were thought to be the dominant charge carrier (Hu et al 2011(Hu et al , 2014.…”

“…The estimation of c act from Eq. (10) has been applied when only a single measurement of diffusion is available, but may lead to considerable variation of c act owing to its small temperature dependence and the experimental uncertainties of diffusion coefficients at various temperatures (Zhang 2012). Consequently, other ways have been proposed to calculate c act , including the compensation law (Zhang et al 2010(Zhang et al , 2011Zhang and Shan 2015a) and the mean value method (Dologlou 2011;Zhang and Wu 2013;Zhang 2014;Zhang and Shan 2015a).…”

“…Notably, a thermodynamic model (termed as the cBΩ model), proposed by Varotsos (1977) and Varotsos and Alexopoulos (1977a, b, 1980a, 1986, Varotsos et al (1978), has been applied to the calculation of defect parameters over a broad range of materials, such as metals, diamond, noble gas solids, fluorides, superionic solids, and viscous liquids (Varotsos and Alexopoulos 1977a, b, 1980b, c, d, 1982, 1986Varotsos et al 1985;Varotsos 2007aVarotsos , b, c, 2008Papathanassiou and Sakellis 2010;Chroneos and Vovk 2015). Recently, its validity has been extended to self-or heterodiffusion in Earth materials (Alexopoulos and Varotsos 1981;Dologlou 2011;Zhang et al 2010Zhang et al , 2011Zhang and Wu 2013;Zhang 2012Zhang , 2014Vallianatos and Saltas 2014;Zhang and Shan 2015a, b;Chroneos and Vovk 2015;Ganniari-Papageorgiou et al 2015;Saltas and Vallianatos 2015). In the present work, our goal is to examine whether the diffusion behaviors of hydrogen and alkali ions in plagioclase feldspars can be reproduced in terms of the bulk and expansivity data based on the recent PVT equation of state of plagioclase feldspars investigated by in situ X-ray diffraction (Angel 2004;Benusa et al 2005;Hovis et al 2010;Tribaudino et al 2010Tribaudino et al , 2011.…”

Application of the cBΩ model to the calculation of diffusion parameters of Si in silicates

“…Thus, such an extrapolation easily introduces an additional uncertainty in the cBΩ model framework. However, previous studies [ Varotsos , ; Zhang et al ., ; Zhang , ] have indicated that the c act value has an uncertainty of not more than 3% mainly because of the experimental error in the elastic and expansivity data determination of solids.…”

Diffusion in garnet: a review

“…Recently, based on the observed MNR, a thermodynamic model (the so-called cBX model) has been successfully applied to predict diffusion coefficients of various elements in silicate minerals (Zhang et al , 2011Zhang 2012;Zhang and Shan 2015a, b).…”