Size-effect on the electronic structure and the thermal stability of a gold nanosolid

Consistent insight into the size-enhanced E_4f-level shift and the size-suppressed melting point of Au nanosolids has been obtained based on the bond order-length-strength (BOLS) correlation mechanism [Sun et al., Acta Mater. 51 (2003) 4631]. Consistency between theory predictions and observations reveals that the atomic-coordination number (CN)-imperfection induced bond contraction and the associated bond energy increase dictate these changes. The increase of binding energy density per unit volume in the relaxed surface region perturbs the Hamiltonian that determines the core-level shift; the decrease of atomic cohesive energy (a product of atomic CN and the single bond energy) determines the thermal energy required for melting. Extending the knowledge to the lower end of the size limit suggests that the metallic bond in the gold monatomic-chain contracts by ∼30% associated with ∼43% magnitude rise of the bond energy. The crystal binding intensity contributing from all the atoms in the solid to the Au-E_4f electrons in the bulk is determined to be -2.87 eV.