### Syntax

`[formfactval, coeff] = sw_cff(atomname, {q})`

### Description

`[formfactval, coeff] = sw_cff(atomname, {q})`

returns the atomic charge
form factors for x-ray scattering. The provided form factor values at Q=0
are normalized to Z.

### Input Arguments

`atomName`

- String, contains the name of the ion in using the symbol of
the element following the charge, e.g.
`'Cr3+'`

. It can be also the coefficients to calculate f. If the string contains whitespace, the first word will be used as input. `Q`

- Momentum transfer in Å\(^{-1}\) units in a matrix with dimensions of \([1\times n_Q]\) or \([3\times n_Q]\), optional.

### Output Arguments

`formFactVal`

- Value of form factor, evaluated at the \(Q\) points if \(Q\) is defined.
`coeff`

- Form factor coefficients according to the following formula: \(f_0(Q_s) = c + \sum_{i=1}^5 a_i\cdot \exp(-b_i Q_s^2)\), where \(Q_s = \frac{Q}{4*\pi}\) and \([a_1, b_1, a_2, b_2, ... c]\) are the coefficients.