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利用量子化学从头算方法,采用RHF/6-31G*和RHF/6-311G*方法,分别研究了六水氯化镁的分子结构与电子结构。计算结果表明,不同的计算方法,所得的结论基本一致,在六水氯化镁模型分子中,两个水分子与氯化镁结合松弛,以RHF/6-311G*计算为例,R[O-Mg]键长分别为0.3972nm和0.3839nm,这两个水分子游离在氯化镁的最外层,结合呈松散状态,极易脱除;另两个水分子与氯化镁结合适中,R[O-Mg]键长分别为0.2142nm和0.2152nm,最后两个水分子与氯化镁结合较牢,R[O-Mg]键长均为0.2081nm,这两个水分子最难脱除。本研究从理论化学的角度合理地解释了六水氯化镁脱水过程的实质,并由此深化对六水氯化镁的内部结构的认识,这种量子化学的计算方法是对现有的六水氯化镁实验研究方法的有益补充。
The molecular structure and electronic structure of magnesium chloride hexahydrate were studied respectively by using ab initio method and RHF / 6-31G * and RHF / 6-311G * methods. The calculated results show that the results obtained by different calculation methods are basically consistent. In the model molecule of magnesium chloride hexahydrate, the two water molecules are loosely bound to the magnesium chloride. Taking the calculation of RHF / 6-311G * as an example, the R [O-Mg] Long 0.3972nm and 0.3839nm respectively. These two water molecules are free from the outermost layer of magnesium chloride. The two water molecules are easy to be removed when they are loosened. The other two water molecules are moderately combined with magnesium chloride. The length of the R [O-Mg] Respectively 0.2142nm and 0.2152nm, the last two water molecules combined with magnesium chloride more firmly, R [O-Mg] bond length 0.2081nm, the two most difficult to remove water molecules. This study reasonably explained the essence of dehydration process of magnesium chloride hexahydrate from the perspective of theoretical chemistry and deepened the understanding of the internal structure of magnesium chloride hexahydrate. This quantum chemistry method is based on the experimental study of existing magnesium chloride hexahydrate A helpful addition to the method.