The valence charge polarization induced by the shorter and stronger bonds between under-coordinated gold atoms

Relativistic density functional theory calculations have been conducted to examine the effect of atomic under-coordination. The calculated results agree exceedingly well with experimental observations: skin-depth bond contraction, chain end stats polarization, potential well depression, core level shift, and the valence charge polarization of gold nanostructures. Consistency between calculations and experimental observations affirms the prediction of the bond-order-length-strength (BOLS) correlation theory [Sun CQ, Phys Rev B 69, 045105 (2004)], asserting that the under-coordinated surface atoms are indeed associated with local strain, quantum trap depression, charge densification and valence charge polarization and that the locally polarized and pinned electrons are responsible for the metal-insulator transition and magnetism present of gold nanoparticles.