NiAs、PbO型FeX (X=S, Se, Te)结构的稳定性与电子特征
The stabilities and electronic properties of NiAs-type and PbO-Type FeX (X=S, Se, and Te)

利用基于密度泛函理论的第一性原理方法, NiAs与PbO型FeX（X=S, Se, Te）结构的稳定性与电子特征得到了研究. 计算结果显示Fe的内聚能与X-Fe元素之间的相互作用是影响FeX结构稳定性的重要因素. 当X 原子半径较小、电负性较大时(X=S), FeX趋向于形成Fe-X相互作用较强、密度较大的NiAs型结构; 当X原子半径较大、电负性较小时(X=Se, Te), FeX趋向于形成Fe-Fe相互作用较强、密度较小的PbO型结构. 此外, 压强使得PbO型FeX结构的稳定性降低. 当压强分别大于5、9 Gpa时, FeTe、FeSe趋向于形成NiAs型结构. PbO型FeSe中Fe原子周围的电子密度随压强的增大而增大.
The structural stabilities and electronic properties of PbO- and NiAs-type FeX (X=S, Se, and Te) were investigated within density functional theory. The calculated results showed that the cohesive energy of Fe atoms and the interactions between Fe and X (X=S, Se, and Te) elements played important roles in the structural stabilities of FeX. For X atoms with smaller radius and higher electronegativity, such as S, FeX preferred to NiAs-type structure which had higher Fe-X bond energy and density than PbO-type structure. On the other hand, when the X atomic radius was larger and its electronegativity was lower, such as Se and Te, the PbO-type structure for FeX was more stable than NiAs-type structure. The PbO-type FeX had higher Fe-Fe bond energy and lower density. In further, it was found that the pressure would decrease the structural stability of PbO-type FeX and make FeSe and FeTe prefer to NiAs-type structure at 9 and 5 GPa, respectively. For PbO-type FeSe, the electronic density around Fe atoms increased with the increasing of pressure.