配合物[Co(SCN)2(HSCN)2(dabco)2]的合成、晶体结构与表征

以SCN-和三乙撑二胺(dabco)为配体,以钴为中心离子采用自组装的方法合成了配合物[Co(SCN)2(HSCN)2(dabco)2],采用单晶X射线衍射、红外光谱、热重分析和元素分析等方法对其进行了晶体结构的解析和表征.它属于单斜晶系,P21/n空间群,晶胞参数分别为a＝0.71964(11)nm,b＝1.12716(17)nm,c＝1.4454(2)nm,β＝96.629(2)°,V＝1.1646(3)nm3,Dc＝1.470 g/cm3,Z＝2,F(000)＝534,μ＝1.115mm-1.热重分析表明,该配合物在530 K以下稳定.     

Different Thermal Stabilities of Cation Point Defects in LaAlO_3 Bulk and Films

Using the first-principles method, we investigate the thermal stability of cation point defects in LaAlO_3 bulk and films. The calculated densities of states indicate that cation vacancies and antisites act as acceptors. The formation energies show that cation vacancies are energetically favorable in bulk LaAlO_3 under O-rich conditions,while the Al_(La) antisites are stable in reducing atmosphere. However, the same behavior does not appear in the case of LaAlO_3 films. For LaO-terminated LaAlO_3 films, La or Al vacancies remain energetically favorable under O-rich and O-deficient conditions. For an AlO_2-terminated surface, under O-rich condition the La interstitial atom is repelled from the outmost layer after optimization, which releases more stress leading to the decrease of total energy of the system. An Al interstitial atom has a smaller radius so that it can stay in distorted films and becomes more stable under O-deficient conditions, and the Al interstitial atoms can be another possible carrier source contribution to the conductivity of n-type interface under an ultrahigh vacuum. La and Al antisites have similar formation energy regardless of oxygen pressure. The results would be helpful to understand the defect structures of LaAlO_3-related materials.