Bond-order–bond-length–bond-strength (bond-OLS) correlation mechanism for the shape-and-size dependence of a nanosolid

A bond-order–bond-length–bond-strength (bond-OLS) correlation mechanism is presented for consistent insight into the origin of the shape-and-size dependence of a nanosolid, aiming to provide guidelines for designing nanomaterials with desired functions. It is proposed that the coordination number imperfection of an atom at a surface causes the remaining bonds of the lower-coordinated surface atom to relax spontaneously; as such, the bond energy rises (in absolute value). The bond energy rise contributes not only to the cohesive energy (E_Coh) of the surface atom but also to the energy density in the relaxed region. E_Coh relates to thermodynamic properties such as self-assembly, phase transition and thermal stability of a nanosolid. The binding energy density rise is responsible for the changes of the system Hamiltonian and related properties, such as the bandgap, core-level shift, phonon frequency and the dielectrics of a nanosolid of which the surface curvature and the portion of surface atoms vary with particle size. The bond-OLS premise, involving no assumptions or freely adjustable parameters, has led to consistency between predictions and experimental observations of a number of outstanding properties of nanosolids.