MOLECULAR-ORBITAL (SCF-X-ALPHA-SW) THEORY OF METAL-METAL CHARGE-TRANSFER PROCESSES IN MINERALS .2. APPLICATION TO FE-2+ GREATER-THAN TI-4+ CHARGE-TRANSFER TRANSITIONS IN OXIDES AND SILICATES
MOLECULAR-ORBITAL (SCF-X-ALPHA-SW) THEORY OF METAL-METAL CHARGE-TRANSFER PROCESSES IN MINERALS .2. APPLICATION TO FE-2+ GREATER-THAN TI-4+ CHARGE-TRANSFER TRANSITIONS IN OXIDES AND SILICATES
复制标题
矿物中金属-金属电荷转移过程的分子轨道（SCF-X-ALPHA-SW）理论 .2。
DOI：
10.1007/bf00309811
复制
发表时间：
1987
影响因子：
1.4
通讯作者：
D. Sherman
中科院分区：
文献类型：
--
作者：
D. Sherman
许多混合价铁氧化物和硅酸盐（例如，Fe 2+和Fe 3+离子间的热致电子离域和Fe 2 +→ Fe 3+的光致电子跃迁是Fe 2 +→ Fe 3+的价间电荷转移过程。极化子与巡游电子）和矿物中光诱导价间电荷转移的性质进行了研究。SCF-Xα-SW分子轨道计算了几个混合价（Fe 2 O 10）15−团簇，对应于边共享的Fe 2+和Fe 3+配位多面体。一个自旋不受限制的形式主义，使相邻的Fe 2+和Fe 3+阳离子的铁磁与反铁磁耦合的效果可以确定。分子轨道的计算结果与固体物理学中的极化子理论以及Robin和Day（1967）等人描述混合价化合物中电子转移的微扰理论有关，Fe（3d）轨道通过相邻FeO 6多面体的共享边重叠产生弱Fe-Fe键，从而导致了价间电荷转移。电子离域，但是，需要相邻的铁离子是铁磁耦合。反铁磁耦合导致Fe ~（2+）和Fe ~（3+）阳离子可区分，Fe-Fe成键轨道和Fe-Fe反键轨道之间的电子跃迁导致混合价矿物电子光谱中出现光诱导价间电荷转移带。这种转变被预测为极化沿着的金属-金属键的方向，与实验观察。
A number of mixed valence iron oxides and silicates (e.g., magnetite, ilvaite) exhibit thermally induced electron delocalization between adjacent Fe2+and Fe3+ions and optically induced electronic transitions which are assigned to Fe2+→Fe3+intervalence charge transfer.In this paper, the mechanism of electron delocalization (i.e., polarons versus itinerant electrons) and the nature of optically induced intervalence charge-transfer in minerals are investigated using molecular orbital theory. SCF-Xα-SW molecular orbital calculations were done for several mixed-valence (Fe2O10)15−clusters corresponding to edgesharing Fe2+and Fe3+coordination polyhedra. A spinunrestricted formalism was used so that the effect of ferromagnetic versus antiferromagnetic coupling of adjacent Fe2+and Fe3+cations could be determined. The molecular orbital results can be related to the polaron theory of solid state physics and the perturbation theory formalism used by Robin and Day (1967) and others to describe electron transfer in mixed valence compounds.Intervalence charge-transfer results from the overlap of Fe(3d) orbitals across the shared edges of adjacent FeO6polyhedra to give weak Fe-Fe bonds. Electron delocalization, however, requires that adjacent Fe cations be ferromagnetically coupled. Antiferromagnetic coupling results in distinguishable Fe2+and Fe3+cations.Electronic transitions between the Fe-Fe bonding and Fe-Fe antibonding orbitals results in the optically-induced intervalence charge transfer bands observed in the electronic spectra of mixed valence minerals. Such transitions are predicted to be polarized along the metal-metal bond direction, in agreement with experimental observations.