In the range of scattering vectors between 0 < q < 25 Å^-1, the atomic form factor is well approximated by the expression, [1]

$\large f(q) \approx \sum\limits_{i=1}^{5} a_i\exp\left(-b_i\left(\frac{q}{4\pi}\right)^2\right),$

where the values of $a_i$, and $b_i$ are tabulated below. The different atomic form factors for the elements can be plotted using the form below.

Electron atomic form factor for H $f(q)$  $q$ [Å-1]

 

Element

a1

b1

a2

b2

a3

b3

a4

b4

a5

b5

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[1] The electron atomic form factors were taken from the International Tables for Crystallography: http://it.iucr.org/Cb/ch4o3v0001/sec4o3o2/.