Anderson-Newns-Grimley model

Here (pi are the Kohn-Sham orbitals and a is a properly chosen localized function, in the present case most suitably the Ru 4d and the O 2p atomic orbitals within a sphere around given atomic sites. According to the Anderson-Grimley-Newns model of chemisorption, the interaction of the O 2p level with the narrow 4d band of the TM surface gives rise to bonding states at the lower edge of the d band and antibonding states at the upper... 

In the effective medium theory, the electronic interaction between an atom and the solid is replaced by that of the atom and a homogeneous electron gas. The approach is based upon density functional theory, but since the solid is not really behaving as a homogeneous electron gas, gradient corrections to the theory have been devised [210]. Simple model hamiltonians have also been used to study chemisorption of atoms and molecules at metals. Here we mention the Anderson-Grimley-Newns model hamiltonian of the type... 

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