Methodologies for size, and temperature dependent change of materials properties

With the miniaturization of a solid down to nanometers scale, the mechanical and optical properties of such nanomaterials are different from that of their corresponding bulk materials. A systematic understanding of the atomic origin of the unusual behavior of mechanical and optical properties of a nanosolid is presented here towards the predictions for design and controllable growth of nanostructured materials. The Local Bond Average (LBA) approximation and bond-order-length-strength (BOLS) correlation mechanism in size, temperature and pressure domain has been developed, which enables the tunability of various measurable properties, such as elastic constants, optical phonon frequency shift. Agreement between predictions and observations reveal that the shortened and strengthened surface bonds are responsible for the observed size dependent change of material properties, while the temperature induced bond expansion and weakening are the physical origin for the temperature dependent change of measurable material properties.