The Energy Decomposition analysis (EDA) is a wavefunction based bonding analysis scheme which enjoys significant popularity in the molecular chemistry community [1,2]. Following an implementation of the method into the periodic structure code BAND [3,4], led recently to the successful characterization of bonds between organic molecules and semiconductor surfaces . It was shown that localized, covalent bonds in a periodic system can be interpreted in a fashion similar to their 0D molecular counterparts. Adsorption of organic molecules on transition metal surfaces, on the other hand, requires a more nuanced description. In addition to covalent bonds, interactions are often characterized by large charge transfer, polarization and dispersion contributions. The inherently delocalized nature of crystal orbitals requires convergence with respect to the size of the k-mesh. Near degenerate states can lead to instabilities in the Natural Orbitals of Chemical Valance [6,7] (NOCV) extension which requires the diagonalization of the deformation density matrix. When the NOCV procedure is successful the orbital interaction term can be further decomposed and analyzed visually. Great care has to be taken when interpreting deformation densities since the influence of band dispersion is only captured in an averaged fashion.References:
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