The atomistic study on the thermal expansion behaviors of nanowires

► Linear expansion is isotropic for bulk and value is 1/3 of volumetric one disregard orientations. ► Thermal expansion coefficient of nanowires is affected by surface and axial crystal orientation. ► Thermal expansion coefficient transits to negative at high temperature for thinnest [1 0 0] nanowires. ► Negative linear thermal expansion is not observed for nanowires along [1 1 0] and [1 1 1] direction. ► Negative thermal expansion behavior is not caused by melting or the phase change from examinations.