Theory BOLS and NEP

Atomic undercoordination shortens and stiffens the remaining bonds between undercoordinated atoms, which follow the BOLS correlation. 

Local densification and quantum entrapment of energy and electrons take places, of which the extent increases with the lowering of atomic CN. Polarization happens to the non-bonding electrons (non-bonding electron polarization, NEP) by the densely entrapped core and bonding electrons, which exemplifies Anderson s localization due to bond order deficiency. 

The polarized electrons neither follow the Hamiltonian nor obey the standard dispersion, but form impurity states in the mid-bandgap region, which splits and screens the local interatomic potentials. 

Core-shell configuration and the local bond average (LBA) are necessary to overcome limitations faced by classical continuum or quantum methods in dealing with the strongly localized nature of undercoordinated atoms. 

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