GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt, Germany.
J Chem Phys. 2012 Jan 21;136(3):034308. doi: 10.1063/1.3676176.
Fully relativistic, four-component density functional theory electronic structure calculations were performed for MBr(5), MOBr(3), MBr(6)(-), KMBr(6), and MBr(5)Cl(-) of group-5 elements Nb, Ta, and element 105, Db, with the aim to predict adsorption behaviour of the bromides in gas-phase chromatography experiments. It was shown that in the atmosphere of HBr/BBr(3), the pentabromides are rather stable, and their stability should increase in the row Nb < Db < Ta. Several mechanisms of adsorption were considered. In the case of adsorption by van der Waals forces, the sequence in volatility of the pentabromides should be Nb < Ta < Db, being in agreement with the sublimation enthalpies of the Nb and Ta pentabromides. In the case of adsorption by chemical forces (on a quartz surface modified with KBr∕KCl), formation of the MBr(5)L(-) (L = Cl, Br) complex should occur, so that the volatility should change in an opposite way, i.e., Nb > Ta > Db. This sequence is in agreement with the one observed in the "one-atom-at-a-time" chromatography experiments. Some other scenarios, such as surface oxide formation were also considered but found to be irrelevant.
采用完全相对论的四分量密度泛函理论对第 5 族元素 Nb、Ta 和 105 号元素 Db 的 MBr(5)、MOBr(3)、MBr(6)(-)、KMBr(6)和 MBr(5)Cl(-)进行了电子结构计算，目的是预测这些溴化物在气相色谱实验中的吸附行为。结果表明，在 HBr/BBr(3)气氛中，五溴化物相当稳定，其稳定性应随 Nb < Db < Ta 增加。考虑了几种吸附机制。在范德华力吸附的情况下，五溴化物的挥发性顺序应为 Nb < Ta < Db，这与 Nb 和 Ta 五溴化物的升华焓一致。在化学力吸附（在 KBr∕KCl 修饰的石英表面上）的情况下，应该形成 MBr(5)L(-)（L = Cl、Br）配合物，因此挥发性应该以相反的方式变化，即 Nb > Ta > Db。这一顺序与“逐个原子”色谱实验中观察到的顺序一致。还考虑了其他一些情况，如表面氧化物的形成，但发现它们并不相关。
