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| - Model Valence-Bond Studies of Aspects of Electron Conduction along a Linear Chain ofLithium Atoms
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| - Two valence bond mechanisms for electron conduction along a linear chain of six or eight lithiumatoms are studied using an ab initio valence bond approach. The initial step is of the type(−)(LiALiB)(LiCLiD)(LiELiF)...(+) → (−)(LiALiB)+(LiCLiD)-(LiELiF)...(+), in which the transferredelectron occupies either the 2pσC atomic orbital (Pauling mechanism) or the antibonding σ*CDmolecular orbital. An external potential is modeled by use of negative and positive charges locatedto the left and to the right of the chain of atoms. It is calculated that (−)(LiLi)+(LiLi)-(LiLi)...(+) →(−)(LiLi)(LiLi)+(LiLi)-...(+), which involves electron and positive hole transfer, as well as(−)(LiLi)+(LiLi)-(LiLi)...(+) → (−)(LiLi)+(LiLi)(LiLi)-...(+), with electron transfer only, contribute tothe second electron transfer process. Resonance between the valence bond structures associated withthe second step helps lower the energy of the second step of either mechanism. The antibonding molecularorbital mechanism is calculated to involve a marginally lower energy than the Pauling mechanism. Theresonance stabilization that occurs in the second step is concomitant with greater positive hole delocalizationthan the first step. This phenomenon is illustrated for a linear polyene by use of Hückel molecular orbitaltheory and the free electron model for electrons in a 1-dimensional box. For both eight-atom mechanisms,the propensity for electron transfer to occur between cathode and anode increases as the size of the externalpotential increases.
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