Polymerisation, basicity, oxidation state and their role in ionic modelling of silicate melts

Polymerisation, basicity, oxidation state and their role in ionic modelling of silicate melts
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聚合、碱度、氧化态及其在硅酸盐熔体离子模拟中的作用

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发表时间：
2005
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通讯作者：
R. Moretti
R. Moretti
中科院分区：
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文献类型：
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作者：
R. Moretti

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为了描述和量化硅酸盐熔体的反应性，Temkin形式主义提供的离子符号 已经被历史上接受，从而引起了熔体化学平衡的研究， 游离的离子种类。事实上，只要熔体的真实延伸，熔体的离子模型就能正常工作。 阴离子基质是已知的。该信息可以在Toop-Samis（1962 a，B）模型的框架中获得， 通过溶解的氧化物的酸碱性质的参数化。此外，通过结合 Toop和Samis的聚合物模型与Duffy和Ingram（1973，1974 a，B， 1976）熔融硅酸盐和玻璃的体光学碱度（Duffy和Ingram，1971; Duffy，1992 分为两个不同的贡献，即溶解的碱性氧化物的碱度和聚合物的碱度。 单位应用于实际情况，如铁的氧化态的评估，需要桥接的 完全离解组分的标准态（Temkin标准态）与 纯熔体组分在感兴趣的P和T下的标准状态。在此基础上，可以建立一个初步 无水和含水铝硅酸盐熔体中铁形态的模型。对于含水熔体，我 引入水组分的酸性和碱性解离，需要H+的组合出现 阳离子、不含OH的阴离子以及在很小程度上的T-OH基团。水的两性行为揭示了 因此，这项研究与Fraser（1975）的早期预测一致。
In order to describe and quantify the reactivity of silicate melts, the ionic notation provided by the Temkin formalism has been historically accepted, giving rise to the study of melt chemical equilibria in terms of completely dissociated ionic species. Indeed, ionic modelling of melts works properly as long as the true extension of the anionic matrix is known. This information may be attained in the framework of the Toop-Samis (1962a,b) model, through a parameterisation of the acid-base properties of the dissolved oxides. Moreover, by combining the polymeric model of Toop and Samis with the «group basicity» concept of Duffy and Ingram (1973, 1974a,b, 1976) the bulk optical basicity (Duffy and Ingram, 1971; Duffy, 1992) of molten silicates and glasses can be split into two distinct contributions, i.e. the basicity of the dissolved basic oxides and the basicity of the polymeric units. Application to practical cases, such as the assessment of the oxidation state of iron, require bridging of the energetic gap between the standard state of completely dissociated component (Temkin standard state) and the standard state of pure melt component at P and T of interest. On this basis it is possible to set up a preliminary model for iron speciation in both anhydrous and hydrous aluminosilicate melts. In the case of hydrous melts, I introduce both acidic and basic dissociation of the water component, requiring the combined occurrence of H+ cations, OH- free anions and, to a very minor extent, of T-OH groups. The amphoteric behaviour of water revealed by this study is therefore in line with the earlier prediction of Fraser (1975).