Ti掺杂NbSe_2电子结构的第一性原理研究

First-principles study on the electronic structure of Ti-doped NbSe_2

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法,计算了理想2H-NbSe_2和Ti掺杂2H-NbSe_2晶体的几何结构及电子结构;对掺杂前后超胞的能带图、态密度及分波态密度图进行了分析.结果表明,掺杂后费米能级附近能量区域的电子态密度出现了较高的峰值,且费米能级位置发生了改变.理论上可以认为Ti的掺杂会使得NbSe_2的导电性增强,有利于开发新型的电接触复合材料.

Layered transition metal dichalcogenides（LTMDs） have renewed interest as electronic materials,but the poor conductivities hinder their further development.Chemical doping can often significantly modify atomic structures and electronic functionalities of a wide range of materials and thus acts as one of the most effective ways to precisely tune material properties for technological application.Here,the geometries and band structures as well as the densities of states of pure NbSe_2 and Ti-doped NbSe_2 nanostructure are studied by employing the ab-initio plane-wave ultra-soft pseudo potential technique based on the density functional theory.We optimize the ground state of NbSe_2 in the layered structure by using the generalized gradient approximation for the exchange-correlation potential.The computational structural parameters are in good agreement with experimental values within 2.5%.To investigate the stability of the doped system with changing the concentration of Ti atoms,2×2×1 2H-NbSe_2 supercells are taken into consideration.Meanwhile,we consider a total of three possible Ti-doping models：substitution,intercalation,and embedded model,and investigate the energy band diagrams,state densities and densities of partial wave state diagram before and after the doping.The results show that the energy electron density of states reaches a higher peak,and the band structure near Fermi level（E_F） is changed obviously,resulting in the variations of the band gap and E_F position and then the increase of electronic conductivity after doping.In addition,our calculations also predict that the electron transport properties can be enhanced by doping Ti and it can be regarded as a useful way to tailor electronic states so as to improve electron transport properties of 2H-NbSe_2.Such a remarkable modification of electronic structure of 2H-NbSe_2by chemical doping offers an additional way of modulating performances of LTMDs and developing new electrical contact composite materials.