The tension and compression of single-crystalline silicon nanowires ͑SiNWs͒ with different cross-sectional shapes are studied systematically using molecular dynamics simulation. The shape effects on the yield stresses are characterized. For the same surface to volume ratio, the circular cross-sectional SiNWs are stronger than the square cross-sectional ones under tensile loading, but reverse happens in compressive loading. With the atoms colored by least-squares atomic local shear strain, the

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... formation processes reveal that the failure modes of incipient yielding are dependent on the loading directions. The SiNWs under tensile loading slip in ͕111͖ surfaces, while the compressive loading leads the SiNWs to slip in the ͕110͖ surfaces. The present results are expected to contribute to the design of the silicon devices in nanosystems.