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Abstract: By applying non-equilibrium Greenʼs functions in combination with the density-functional theory, we investigate the transport behavior of molecular devices composed by metal electrode–C60 molecule–metal electrode. Our results show that the electronic transport properties are affected obviously by the different contact distances between the electrodes, and the tunneling current decreases approximately exponentially at a certain bias with the increasing of contact distances. The negative differential resistance is observed and the peak-to-valley ratio can be tuned by different contact distances. The mechanisms of the contact distance effect and the negative differential resistance behavior are proposed. [Copyright &y& Elsevier]