Modelling of substitutional defects in the structure of Ti-bearing hibonite

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• 作者：I. A. Pankin ; A. N. Kravtsova ; O. E. Polozhentsev…
• 关键词：local atomic structure ; geological materials ; hibonite ; computer modeling ; density functional theory ; XANES spectroscopy
• 刊名：Journal of Structural Chemistry
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：57
• 期：7
• 页码：1369-1376
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Inorganic Chemistry; Physical Chemistry; Atomic, Molecular, Optical and Plasma Physics; Atomic/Molecular Structure and Spectra; Solid State Physics;
• 出版者：Pleiades Publishing
• ISSN：1573-8779
• 卷排序：57

文摘

A local atomic structure around titanium positions in Ti-bearing hibonite (CaAl₁₂O₁₉) has been studied. The structural models of substitution of different substitution defects Ti–Al in hibonite by titanium atoms have been considered. Optimization of structural models of hibonite has been done by means of density functional theory calculations using pseudopotential approximation as implemented in VASP 5.3 code. Gibbs free energies analysis has shown that models of substitution of M2 and M4 aluminum positions by titanium atoms are the most probable. For the most probable structural models of Ti-bearing hibonite theoretical X-ray absorption near-edge structure (XANES) spectra near the titanium K edge have been calculated. Significant differences in theoretical XANES spectra calculated for different structural models with non-optimized and optimized atomic structure have been demonstrated. Changes in the intensity of pre-edge structure of TiK XANES spectra for different substitution models of aluminum by titanium have been observed which relate to different titanium coordination in structural models. Energy shift of spectral features towards lower energy for optimized models implies increase of interatomic distances in local surroundings of Ti absorbing atoms.