The negative electron affinity of polyethylene well established experimentally is investigated theoretically by first-principles electronic structure calculations. We hypothesize that the nature of the lowest conduction band could be interchain,instead of intrachain, explaining the negative electron affinity. We focus in particular on the nature of states on either sides of the band gap, and on their behavior for variable interchain spacing. Preliminary results indicate that while the valencebands are clearly intrachain, the lowest conduction band in fact appears to display an interchain character extending about 5 A away from the chain. The consequences on the possible formation mechanism of space charge region are discussed.
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