Approximations for the exchange potential in electron scattering

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Abstract
Four new exchange potentials (the semiclassical exchange approximation, the asymptotically adjusted free‐electron–gas exchange approximation, the second‐order free‐electron–gas exchange approximation, and the high‐energy exchange approximation) are derived. Calculations are performed for elastic electron scattering from helium and argon. The results are compared to one another and to calculations using Hara’s free‐electron–gas approximation and the exact nonlocal exchange potential. Three of the approximations to exchange are in good agreement with the exact exchange —except at very low energy— but are much easier to use. Thus they should be very useful in electron–atom and electron–molecule scattering calculations.