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F(000)

  • Page ID
    17706
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    The expression for a structure factor evaluated in the zeroth-order case h = k = l = 0 yields the result

    F(000) = [ (\sum f_{r} )^{\,2} + (\sum f_{i}
)^{\,2} ]^{1/2}

    where fr is the real part of the scattering factors at \(\theta = 0^\circ\), fi is the imaginary part of the scattering factors at \(\theta = 0^\circ\), θ is the Bragg angle, and the sum is taken over each atom in the unit cell.

    F(000) is computed without dispersion effects in electron-density calculation by Fourier inversion. In all cases, non-dispersive F(000) is a structure factor and not a structure amplitude: it has both magnitude and a sign.

    For X-rays non-dispersive F(000) is positive definite and in many cases an integer (but it is not an integer for non-stoichiometric compounds). It counts the number of electrons in the cell.

    For neutrons non-dispersive F(000) is either positive or negative and counts the total nuclear scattering power in the cell.


    F(000) is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Online Dictionary of Crystallography.

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