用从头算法研究高氯酸钠溶液中存在的离子缔合物种及缔合过程

Ab-initio Investigation on Ion-associated Species and Association Process in NaClO_4 Solution

采用量子化学计算方法在HF/6-31+G*水平下对高氯酸钠溶液中可能存在的离子缔合物种及浓度升高时溶液中发生的离子缔合过程进行了研究.高氯酸根与水合钠离子可形成溶剂共享离子对、接触离子对、三离子及多离子团簇等离子缔合物种,当体系中水比较充足时,钠离子可以保持较规整的六配位八面体构型,而当水分子比较少时,则生成不规则的五配位构型.以上水合离子缔合物种中的ν1-ClO4-频率与水合硝酸根中的参比值相比,分别发生4.7,8.5及14～17cm-1的蓝移,除以影响因子后,其与实验结果符合得很好.通过将计算结果与实验结果进行对比,高氯酸钠溶液在浓度升高时发生离子缔合的过程可简略表示为"自由水合离子→溶剂共享型离子对→单齿接触离子对→阳-阴-阳型三离子团簇→链状多离子团簇→网状多离子团簇→无定形晶体".这个过程与硫酸镁相似,而与硝酸镁、高氯酸镁和硝酸钠不同.

The associated species and process in the NaClO4 solution were investigated at the HF/6-31＋G^＊ level.The ClO4^- ions binding with hydrated Na^＋ ions can form solvent-shared ion pairing,contact ion pairing and multiple（including triple） ion clusters.When there are abundant water molecules,the regular octahedral hexacoordinated structure of Na＋ ion can be kept while the irregular penta-and tetra-coordinated structures will form with lacking water.The ν1-ClO-4 frequencies in the species above are 4.7,8.5 and 14—17 cm-1 larger than the reference value in hydrated ClO4^-,which is corresponding with the results in experiment after multiplied by a scale factor.The associated process in the NaClO4 solution can be expressed as ＂free hydrated ion→solvent-shared ion pairing→mono-dentate contact ion pairing→cation-anion-cation triple ion cluster→catenulate multiple ion cluster→reticular multiple ion cluster→amorphous crystal＂.The process is not analogous with those in the Mg（NO3）2,Mg（ClO4）2 and NaNO3 systems but the MgSO4 system.