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The resistance of an atomic Na wire between two macroscopic metallic electrodes is found to decrease by a factor of 2 going from the 1- to the 2-atom wire, and then to stay roughly the same for the 2-, 3-, and 4-atom wires. The initial decrease in resistance is related to the phenomenon of incomplete valence resonances for an atom interacting with a continuum of states. Such resonances lead to what might be called incomplete conduction channels.
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N. D. Lang (1997) studied this question.
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