The electronic and magnetic properties of Ti–Fe defects substitution for two adjacent aluminum ions in blue kyanite with various spin configurations, charges, and alignments have been investigated using first-principles calculations based on density functional theory. Based on the total-energy calculations, we find two possible ground-state spin configurations: high-spin states of Ti^IV–Fe^II and Ti^III–Fe^III with anti-ferromagnetic alignment between Ti and Fe. Among all spin states and alignments, the high-spin state of Ti^IV–Fe^II type-IV alignment is the lowest energy configuration. The optical excitation energy of the high-spin state of Ti^IV–Fe^II calculated from the highest occupied Fe state to the lowest unoccupied Ti state is 1.48 eV, lying in the infrared region of the solar spectrum. Owing to the infrared absorption of Ti–Fe defects, these defects are unlikely to be responsible for the origin of the blue color in kyanite. We, therefore, suggest that other defects or mechanisms may be responsible for the blue coloration in kyanite.

使用基于密度泛函理论的第一性原理研究了蓝晶石中具有不同自旋构型，电荷和取向的两个相邻铝离子的Ti-Fe缺陷的电子和磁性性质。根据总能量计算，我们发现两种可能的基态自旋结构：Ti ^IV -Fe ^II和Ti ^III -Fe ^III的高自旋态，并且在Ti和Fe之间反铁磁排列。在所有自旋态和取向中，Ti ^IV –Fe ^II型IV取向的高自旋态是最低的能量构型。Ti ^IV -Fe高自旋态的光激发能从最高占据的Fe态到最低的未占据的Ti态计算得出的^II为1.48 eV，位于太阳光谱的红外区域。由于Ti-Fe缺陷的红外吸收，这些缺陷不太可能是蓝晶石中蓝色起源的原因。因此，我们建议，其他缺陷或机理可能是蓝晶石中蓝色的原因。