Computational results of Au–Au–Au junction. The three I–V curves are (a) spin-up current, (b) spin-down current, and (c) total current at different distances. Panel (d) is the spin polarization P at the distance of 3.5 Å. Panels (e)–(g) are the projected density of state (PDOS) of the center Au atom at the distance of (e) 3.2 Å, (f) 3.5 Å, and (g) 3.8 Å, respectively. In panels (e)–(g), solid lines represent the PDOS of spin-up electron, dot lines represent the PDOS of spin-down electron, and the vertical dash lines represent Fermi energy (e) −6.4576 eV, (f) −6.3031 eV, and (g) −6.2303 eV, respectively.