利用密度泛函理论，在B3LYP/6‐311＋＋G（d ，p）基组水平上对吡啶‐水团簇（C5H5N）n（H2O）m（n＝1～2，m＝1～4）的可能构型进行全优化，得到了团簇的稳定结构；计算结果显示，在吡啶和水的二聚体中，稳定构型只有一种，没有发现通过π氢键（O— H…π）作用形成的团簇结构。为了研究各团簇结构的稳定性，在相同的基组水平上计算得到了各团簇构型的总能量和结合能，结果显示，对于团簇（C5 H5 N ）n （H2 O ）4（n＝1～2），团簇中的水分子形成四元环的结构要比形成三元环的结构稳定。对团簇的最高占据轨道与最低空轨道之间的能隙分析发现，团簇C5 H5 N （H2 O ）4的最低能量结构具有较高的稳定性，可能具有幻数结构；最后，分析讨论了吡啶‐水团簇的红外振动光谱，对较强的谱峰进行了指认。
We investigate the Rashba and Dressehaus spin-orbit(SO)couplings in an ordinary GaAs/AlGaAs asymmetric double well,which favors the electron occupancy of three subbands v=1,2,3.Resorting to an external gate,which adjusts the electron occupancy and the well symmetry,we demonstrate distinct three-level SO control of both Rashba(αv)and Dresselhaus(βv)intraband terms.Remarkably,as the gate varies,the first-subband SO parametersα1 andβ1 comply with the usual linear behavior,whileα2(β2)andα3(β3)respectively for the second and third subbands interchange the values,triggered by a gate controlled band swapping.This provides a pathway towards fascinating selective SO control in spintronic applications.Moreover,we observe that the interband Rashba(ημv)and Dresselhaus(Lμv)terms also exhibit contrasting gate dependence.Our results should stimulate experiments probing SO couplings in multi-subband wells and adopting relevant SO features in future spintronic devices.
