Chemical Bonding Analysis
Chemical bonding analysis extracts bond-level information from periodic electronic structure calculations. The crystal orbital Hamilton population (COHP), often computed with LOBSTER from plane-wave DFT, weights the density of states by Hamiltonian matrix elements between atomic orbitals so that each energy can be classified as bonding or antibonding for a given pair of atoms; integrated COHPs serve as heuristic measures of covalent bond strength. COHP-derived metal-oxygen covalency is also used as a stability descriptor in doped oxides.
Bonding to antibonding transitions behind elastic trends in Ta-W (2026)
Abdelmaqsoud, Kitchin and Widom used orbital-resolved COHPs for nearest- and next-nearest-neighbor Ta-W pairs in B2 TaW to explain the composition dependence of the elastic constants. Nearest-neighbor bonding, chiefly T2g-T2g, is strong at low valence electron count and becomes weakly antibonding at high count, while next-nearest-neighbor interactions go from strongly to weakly antibonding; all of these changes occur near a T2g degeneracy at the Gamma point 0.12 eV above the equiatomic Fermi level. Combined with real-space wave function plots, this connects the filling of particular orbitals to the stiffening of C11 and the shear moduli on the W-rich side (Abdelmaqsoud et al. 2026). Summary: abdelmaqsoud2026a.