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Structural properties of iron-phosphate glasses: spectroscopic studies and ab initio simulations

机译：磷酸铁玻璃的结构特性：光谱研究和从头算

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摘要

Vitrification is the most effective method for the immobilization of hazardous waste by incorporating toxic elements into a glass structure. Iron phosphate glasses are presently being considered as matrices for the storage of radioactive waste, even of those which cannot be vitrified using conventional borosilicate waste glass. In this study, a structural model of 60P2O5-40Fe2O3 glass is proposed. The model is based on the crystal structure of FePO4 which is composed of [Fe04][P04] tetrahedral rings. The rings are optimized using the DFT method and the obtained theoretical FTIR and Raman spectra are being compared with their experimental counterparts. Moreover, the proposed model is in very good agreement with X-ray absorption fine structure spectroscopy (XANES/EXAFS) and Mossbauer spectroscopy measurements. According to the calculations the Fe~(3+) is in tetrahedral and five-fold coordination. The maximal predicted load of waste constituents into the glass without rebuilding of the structure is 30 mol%. Below this content, waste constituents balance the charge of [FeO4]~-tetrahedra which leads to their strong bonding to the glass resulting in an increase of the chemical durability, transformation and melting temperatures and density.
机译：通过将有毒元素掺入玻璃结构中，玻璃化是固定危险废物的最有效方法。目前，磷酸铁玻璃被认为是用于存储放射性废物的基质，即使是那些不能使用常规硼硅酸盐废玻璃进行玻璃化的基质。在这项研究中，提出了一种60P2O5-40Fe2O3玻璃的结构模型。该模型基于FePO4的晶体结构，该晶体由[Fe04] [P04]四面体环组成。使用DFT方法对环进行了优化，并将获得的理论FTIR和拉曼光谱与其实验对应物进行比较。此外，所提出的模型与X射线吸收精细结构光谱（XANES / EXAFS）和Mossbauer光谱测量非常吻合。根据计算，Fe〜（3+）呈四面体和五重配位。在不重建结构的情况下，废物成分进入玻璃的最大预计负荷为30摩尔％。低于此含量，废料成分平衡[FeO4]〜-四面体的电荷，这导致它们与玻璃的牢固结合，从而导致化学耐久性，相变以及熔融温度和密度的增加。

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