Electronic structure and magnetic properties of(Cu,N)-codoped3C-SiC studied by first-principles calculations

The electronic structures and magnetic properties of the Cu and N codoped 3C-Si C system have been investigated by the first-principles calculation.The results show that the Cu doped Si C system prefers the anti-ferromagnetic(AFM) state.Compared to the Cu doped system,the ionicities of C–Cu and C–Si in Cu and N codoped Si C are respectively enhanced and weakened.Especially,the Cu and N codoped Si C systems favor the ferromagnetic(FM) coupling.The FM interactions can be explained by virtual hopping.However,higher N concentration will weaken the ferromagnetism.In order to keep the FM interaction,the N concentration should be restricted within 9.3% according to our analysis.     

Nb掺杂γ-TiAl金属间化合物的电子结构与力学性能

运用基于密度泛函理论的第一性原理方法计算了Nb掺杂γ-TiAl金属间化合物的结构参数、能带结构、电子态密度及弹性常数.结果表明:Nb替代Ti掺杂相比Nb替代Al掺杂的形成能低,Nb在替位掺杂时更倾向于取代Ti原子形成稳定的结构,Nb替代Ti掺杂能够提高γ-TiAl金属间化合物的抵御塑性变形能力、断裂强度和延展性;与Nb替代Ti掺杂相比,Nb替代Al掺杂同样增强γ-TiAl金属间化合物的断裂强度且其增强延展性的效果更好,但抵御塑性变形的能力有所削弱.     

氧化锌掺钡的电子结构及其铁电性能研究

运用基于密度泛函理论的第一性原理方法计算了不同原子百分比含量的Ba掺杂Zn0半导体体材料超晶胞的能带结构、电子态密度、极化率和相对介电值.计算结果表明:Ba掺杂的Zn0体系为直接带隙半导体材料,其禁带宽度随着Ba原子掺杂百分比的增加呈现出逐渐增大的趋势.体系铁电性能的计算表明:与纯Zn0相比,Zn0掺入Ba原子后的极化率与相对介电值发生了较为明显的变化,其极化率随着Ba原子掺杂百分比的增加而增大,相对介电值随着Ba原子掺杂百分比的增加而减小.对角化后的极化率分量的数值结果表明:在电场作用下超胞中可能存在微畴结构,并且由于畴间电偶极矩的强相互作用,使得超胞宏观上表现为几乎具有各向同性的极化率特征.