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利用量子化学计算方法,在HF/6-31+G*水平下对硝酸锂溶液中可能存在的离子缔合物种,以及当浓度升高时溶液中发生的离子缔合过程进行了研究.硝酸根与水合锂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,在所有的缔合物种中,锂离子大都以形成四配位四面体结构为主,只有少数情况下存在能量较高的五配位结构.以上3种水合离子缔合物种中的v1(NO3-)频率与水合硝酸根中的参比值相比,分别发生1.4,-6.9以及大于2.8 cm-1的蓝移,考虑到实验光谱中v1(NO3-)带是持续蓝移的.推测的硝酸锂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→阳-阴-阳型三离子团簇→链状多离子团簇→网状多离子团簇→晶体”.这个过程与在硝酸镁和硝酸钠中的缔合过程是相似的.
Ion-association species that may be present in lithium nitrate solution at HF / 6-31 + G * levels and ion-association processes that occur in solution at elevated concentrations are studied using quantum chemistry calculations. Nitrate With hydrated lithium ions can form solvent-sharing ion pairs, contact ion pairs, three ions and multi-ion cluster plasma association species, in all associated species, most of the lithium ions to form tetrahedral tetrahedral structure, only In rare cases, there is a pentacoordinate structure with higher energies. The frequencies of v1 (NO3-) in the above three hydrated ion-association species are 1.4, -6.9 and more than 2.8 cm, respectively, compared with the reference values in hydrated nitrate -1 blue shift, taking into account the experimental spectrum in the v1 (NO3-) band is a continuous blue shift.Prediction lithium nitrate solution at high concentrations of ion association occurs when the process can be briefly expressed as “free hydrated ions to solvent Shared ion pair → positive-negative-positive three ion cluster → chain polyionic cluster → network polyionic cluster → crystal. ”This process is similar to the association process in magnesium nitrate and sodium nitrate of.