To show the field enhancement effect, we calculate the absorption spectra and near fields of the truncated Au tetrahedrons with different side lengths of 2.88 nm, 4.32 nm, and 5.76 nm in Figure The near field decays rapidly with the surface separation as Figure shows. To have a clear picture on the effect of the near field's inhomogeneity on the water splitting, we perform the TDDFT/Ehrenfest dynamics of Au 20 @H 2 O interacted with the real near field generated by the truncated Au tetrahedron with L=2.88 nm and the uniform electric field taken from the center of mass of Au 20 @H 2 O generated by the same NP, respectively.