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分别用量子化学MNDO和DV-X_α方法计算了二聚铝酸离子[Al_2O(OH)_6]~(2-)和Al(OH)_4~-。结果表明前者旋转势垒很低,只有10.08kJ·mol~(-1),最稳定平衡构型为C_s。用X_α过渡态理论计算获得这两个离子紫外吸收峰的理论值分别为2666A和2344A,与实验值2700A和2300A相当接近。因此可以认为,紫外吸收峰2700A和2300A分别为[Al_2O(OH)_6]~(2-)和Al(OH)_4~-离子的最高占有轨道电子向最低空轨道跃迁时产生的吸收峰。计算结果支持铝酸钠溶液中存在二聚铝酸离子的观点。
The dimeric aluminate ions [Al_2O (OH) _6] ~ (2-) and Al (OH) _4 ~ - were calculated by using quantum chemical method MNDO and DV-X_α respectively. The results show that the former has a very low rotational barrier of only 10.08 kJ · mol ~ (-1) and the most stable equilibrium configuration is C_s. The theoretical values of UV absorption of these two ions calculated by X_α transition state theory are 2666A and 2344A respectively, which are quite close to the experimental values of 2700A and 2300A. Therefore, UV absorption peaks 2700A and 2300A can be considered as the absorption peaks of the highest occupied orbital electrons of [Al_2O (OH) _6] ~ (2-) and Al (OH) _4 ~ The results support the view that dimerization aluminate ions are present in the sodium aluminate solution.