Size and confinement effect on nanostructures

TL;DR

This paper introduces a bond order-length-strength (BOLS) correlation mechanism that explains and predicts the size and surface effects on various properties of nanostructures, validated by experimental data.

Contribution

The development of the BOLS correlation mechanism provides a unified theoretical framework for understanding and controlling nanostructure properties based on atomic coordination effects.

Findings

Bond contraction at low-coordination sites enhances local energy density.

The BOLS model accurately predicts property changes in nanostructures.

Experimental verification supports the validity of the BOLS correlation.

Abstract

This report presents a systematic understanding of the nature behind the unusual behavior of a nanosolid, and a surface as well, in mechanics, thermodynamics, acoustics, optoelectronics, magnetism, dielectrics, atomic diffusivity and chemical reactivity towards predictable design and controllable growth of nanostructured materials. A bond order-length-strength (BOLS) correlation mechanism has been developed, which has enabled the tunability of a variety of properties of a nanosolid in connection with surface to be consistently predicted and experimentally verified. The BOLS correlation indicates that the coordination number (CN) imperfection of an atom at site surrounding a defect or in the surface skin causes the remaining bonds of the lower-coordinated atom to contract spontaneously. The spontaneous bond contraction is associated with bond-strength gain or atomic potential well deppression, which localize electrons and enhance the density of charge, mass, and energy in the relaxed region. The enhancement of energy density in the relaxed region perturbs the Hamiltonian and the associated properties such as the band-gap width, core-level energy, Stokes shift (electron-phonon interaction), and dielectric susceptibility. On the other hand, bond order loss lowers generally the cohesive energy of the lower-coordinated atom from the value of a fully-coordinated atom, which dictates the thermodynamic process such as self-assembly growth, atomic vibration, thermal stability, and activation energies for atomic dislocation and diffusion. Consistency between predictions and observations evidences the enormous impact of atomic CN imperfection and the validity and essentiality of the BOLS correlation.