ZnO meso-mechano-thermo physical chemistry

From the perspectives of bond order-length-strength (BOLS) correlation and nonbonding electron polarization (NEP), we have correlated the elasticity, band gap, phonon frequency, thermal stability, dilute magnetism, hydrophobicity, and the enhanced catalytic ability of ZnO with formulation of their size, temperature, and pressure dependence using the local-bond average (LBA) approach. The detectable quantities are functionally correlated to the order, nature, length, and energy of the representative bond of the entire specimen and its response to applied stimuli. Bond-order loss causes the bonds between the under-coordinated atoms to contract spontaneously associated with bond strength gain and interatomic trapping-potential-well depression. Therefore, the increase of the bond energy and binding energy density, reduction of atomic cohesive energy, localized densification of charge, energy, and mass occurring to the surface of skin depth, which dominate the property change of ZnO nanostructures as a function of size. Consequently, the increase of energy density augments the Young’s modulus; the increase of bond energy enhances the Hamiltonian that determines the band gap expansion and the electron-phonon interaction, or the Stokes shift; the drop of atomic cohesive energy lowers the critical temperatures for melting and nucleation growth as well as the phonon relaxation dynamics; the polarization of the unpaired nonbonding electrons by the densely-and-locally entrapped core charge originates the dilute magnetism, superhydrophobicity, and the enhanced catalytic ability. Varying pressure and temperature also alters the bond length and energy and hence the physical properties of ZnO in a predictable way.