中文摘要：

本文利用密度泛函理论结合非平衡格林函数的方法,对（GaAs）n（n=1—4）直线原子链与Au（100）-3×3两半无限电极耦合构成Au-（GaAs）n-Au纳米结点的电子输运性质进行了第一性原理计算.在各结点拉伸过程中,对其结构进行了优化,得到各结点稳定平衡结构时Ga—As的平均键长分别为0.220,0.224,0.223,0.223 nm,平衡电导分别为2.328G0,1.167G0,0.639G0,1.237G0;通过对结点投影态密度的计算,发现电子传输主要是通过Ga,As原子中px与py电子轨道相互作用形成的π键进行的.在0—2 V的电压范围内,对于（GaAs）n（n=1—3）的原子链的电流随电压增大而增大,I-V曲线呈线性关系,表现出类似金属导电行为;对于（GaAs）4原子链在0.6—0.7 V,0.8—0.9 V的电压范围内却存在负微分电阻现象.

英文摘要：

Electron transport properties of the（GaAs）n（n = 1–4）linear atomic chains,which are sandwiched between two infinite Au（100）-3×3 leads,are investigated with a combination of density functional theory and non-equilibrium Green＇s function method from first principle.We simulate the Au-（GaAs）n-Au nanoscale junctions breaking process,optimize the geometric structures of four kinds of junctions,calculate the cohesion energies and equilibrium conductances of junctions at different distances.The calculation results show that there is a stable structure for each nanoscale junction.The average bond-lengths of Ga-As in each chain at equilibrium positions for stable structure are 0.220 nm,0.224 nm,0.223 nm,0.223 nm,respectively.The corresponding equilibrium conductances are 2.328G0,1.167G0,0.639G0,and1.237G0,respectively.It means that each of all the junctions has a good conductivity.We calculate the transmission spectra of the all the chains.With the increase of atomic number in the（GaAs）n（n = 1–4）chains,there appears no oscillation phenomenon for the equilibrium conductance.We calculate the projected densities of states of all nanoscale junctions at equilibrium positions,and the results show that electronic transport channel is mainly contributed by the pxand pyorbital electrons of Ga and As atoms.In the voltage range of 0–2 V,we calculate the current-voltage characteristics of junctions at equilibrium positions.With the increase of external bias,the current increases,and the I-V curves of junctions show linear characteristics for the（GaAs）n（n = 1–3）atomic chains.However,there appears a negative differential resistance phenomenon in each of the voltage ranges of 0.6–0.7 V and 0.8–0.9 V for the（GaAs）4linear atomic chain.