Mechanical properties and micro-structure fracture mechanism of tungsten nanowires with crystal orientation of [110],[112] and [111] have been investigated with molecular dynamics and embedded atom methods. Simultaneously common neighbor analysis, center symmetry parameters and coordination number has been employed to analysis the evolution of structure. It is concluded that different crystal orientation nanowires have different characters. The elastic modulus, yield strain, yield strength and the fracture stress is decreasing in the sequence of[111], [110]and [112] crystal orientations. It also reveal that all of the stress-strain curves are classified into four stages: elastic stage, damage stage, yielding stage and failure stage. It concluded that crystal orientation has slightly impact on the elastic modulus but has great effect on tensile strength, yield strength and ductility. Interestingly, hardening stage has been found in tungsten nanowire with crystal orientation of [112] at yielding stage. That is to say the strain increase with the stess increase in the hardening stage, the nanowire with crystal orientation of [112] has the trend that recover its capability in strength, but consequently result in the least ductility. In the end the tensile failure mechanisms of the three nanowires have been summarized. Key Words: molecular dynamics; stress?strain curve; tungsten nanowire; crystal orientation
