中文摘要：

采用基于密度泛函（DFT）的非平衡态格林函数方法（non-equilibrium Green functions,NEGF）,讨论电极距离对分子电子结构和电流的影响,计算四种脱氧核苷酸的I-V特性曲线和透射谱.结果表明,电极距离小于1.55nm时,电极距离对脱氧核苷酸分子的电子结构影响较大,当电极距离大于1.55nm时,LUMO和HOMO附近各能级的变化趋于平缓,电子能隙变化非常小.电极距离固定时,较低偏压（0.1～0.8V）不会改变四种脱氧核苷酸分子的相对电流大小.偏压较大时（0.8～1.0V）,T和C的电流迅速增加并远大于A和G.

英文摘要：

With density functional theory and non-equilibrium Green function method,we calculate I-V characteristics and transmission spectra of deoxyribonucleotides under low bias.Effect of electrode distance on transverse electronic transport is discussed.As distance between electrodes is less than 1.55 nm,it shows great influence on electronic structures.As the distance is more than 1.55 nm,the energy level near LUMO and HOMO changes slowly and the variation of LUMO-HOMO gap is very small.At a fixed distance between electrodes,the relative current of deoxynucleotides is not changed with lower biases （0.1 ～ 0.8 V）.The current of T and C increases rapidly and is greater than that of A and G as the bias increases from 0.8 to 1.0 V.