Chemisorption on Monatomic Substrate

The system we wish to investigate consists of a single atom a interacting with a semi-infinite monatomic chain. The site (bond) energy of the chain is a( ), while that of the a-atom is aa (fja). Initially, the substrate is represented by a cyclic chain of N atoms, whose GF is given by (2.49). A semi-infinite chain is then formed by breaking the bond between the n = 0 and N — 1 atoms (Fig. 3.1). 

Mathematically, this is achieved by means of the Dyson operator equation (3.3), in which Go(G) denotes the Greenian of the cyclic (semi-infinite) chain, and the bond-breaking potential operator is given by 

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