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We show the reconciliation of the strain ( ε )-, pressure ( P )-, and layer-number ( N )-dependence of the phonon frequency and photon energy shifts for MX 2 in terms of stimulated bond relaxation, with quantification of the coefficients of bond length and energy relaxation, the bond nature index, force constant, and cohesive energy density. We found that (i) atomic under-coordination shortens and stiffens the M–X bond, which widens the bandgap; (ii) the directional strain governs phonon-frequency splitting and narrowing; and (iii) homogenous mechanical compression induces the opposite effect of stretching. [ABSTRACT FROM AUTHOR]

We examined the combined effect of atomic under- and hetero-coordination on the bond relaxation and electronic binding energy of Sc, Zr, and ScZr alloying using a combination of the bond-order–length–strength (BOLS) correlation and density functional theory (DFT) calculations. Observations strongly emphasize the relevance of core-level shifts as reliable X-ray photoelectron spectroscopy experimental descriptors of core–shell catalysis reactivity, along with under-coordinated atoms in bimetallic transition metal systems. The BOLS–DFT method provides enhanced catalysis reactivity and detects surface and alloy configurations, opening up the possibility to investigate more complex systems with irregularly under- and hetero-coordinated atoms. [ABSTRACT FROM AUTHOR]

A combination of the photoelectron spectrometrics and density functional theory calculations has confirmed bond-order-length-strength (BOLS) predictions on the atomic undercoordination induced local bond contraction, charge densification and bond energy entrapment of lithium (Li) atomic clusters and layer-resolved Li(1 1 0) skins. Analysis also derives the energy level of an isolated Li atom and its shift upon bulk and skin formation, which is beyond the scope of currently available approaches. [ABSTRACT FROM AUTHOR]