Radiotracer Experiments and Monte Carlo Simulations of Sodium Diffusion in Alkali Feldspar: Evidence against the Vacancy Mechanism
Radiotracer Experiments and Monte Carlo Simulations of Sodium Diffusion in Alkali Feldspar: Evidence against the Vacancy Mechanism
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DOI：
10.4028/www.scientific.net/ddf.363.79
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发表时间：
2015-05
影响因子：
--
通讯作者：
F. Wilangowski;R. Abart;S. Divinski;N. Stolwijk
中科院分区：
文献类型：
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作者：
F. Wilangowski;R. Abart;S. Divinski;N. Stolwijk
用自扩散实验和Monte Carlo模拟方法研究了钠在富钾碱长石晶体中垂直于（001）方向的自扩散。用22 Na同位素示踪技术测量了773 ~ 1173 K温度区间内的钠扩散系数。结果表明，自扩散系数与指前因子呈线性关系，指前因子为1：2 × 103 cm ~ 2/s，自扩散激活焓为1：3eV。为了研究单斜长石结构中的相关效应，应用Monte Carlo方法，假设两种阳离子物种随机分布在共同的亚晶格上，并且不受硅酸盐和铝酸盐阴离子的固定亚晶格的影响。相关因子已被计算assuminga空位机制和应用开发的四频模型的最近邻空位跳跃的碱性亚晶格。我们的研究结果强烈表明，空位扩散providedonly一个微小的贡献，钠的自扩散在富钾长石。
Self-diffusion of sodium perpendicular to (001) in a potassium-rich alkali feldspar singlecrystal has been studied by self-diffusion experiments and by Monte Carlo simulations. Sodium diffusivitieswere measured with the radiotracer technique using the 22Na isotope in a temperature intervalfrom 773 K to 1173 K. It was found that self-diffusion coefficients follow a linear Arrhenius relationwith the pre-exponential factor of 1:2 103 cm2/s and an activation enthalpy of 1:3 eV. To study correlationeffects in the monoclinic feldspar structure, a Monte Carlo method was applied assuming thatthe two cation species are randomly distributed on the common sublattice and are not influenced by thefixed sublattice of the silicate and aluminate anions. Correlation factors have been calculated assuminga vacancy mechanism and applying a developed four-frequency model for the nearest-neighborvacancy jumps on the alkali sublattice. Our findings strongly indicate that vacancy diffusion providesonly a minor contribution to sodium self-diffusion in potassium-rich feldspars.