This paper have performed molecular static calculations with the quantum corrected Sutten-Chen type many body potential to study size effects on the elastic modulus of Au nanowires with [100],[110] and [111] crystallographic directions,and to explore the preferential growth orientation of Au nanowires. The main focus of this work is the size effects on their surface characteristics. Using the common neighbour analysis,this paper deduces that surface region approximately consists of two layer atoms. Further,it extracts the elastic modulus of surface,and calculate surface energy of nanowire. The results show that for all three directions the Young's modulus of nanowire increases as the diameter increases. Similar trend has been observed for the Young's modulus of surface. However,the atomic average potential energy of nanowire shows an opposite change. Both the potential and surface energy of [110] nanowire are the lowest among all three orientational nanowires,which helps to explain why Au nanowires possess a [110] preferred orientation during the experimental growth proceeds.
