\(\renewcommand\AA{\text{Å}}\)

# X-ray scattering factor f0 calculations

## `periodictable.cromermann`

Cromer-Mann formula for calculating x-ray scattering factors.

class periodictable.cromermann.CromerMannFormula(symbol, a, b, c)

  Bases: `object`

  Cromer-Mann formula for x-ray scattering factors. Coefficient storage and evaluation.

  Class data:

  stollimit float | Å-1

    maximum sin(theta)/lambda for which the formula works

  Attributes:

  symbol string

    symbol of an element

  a[float]

    a-coefficients

  b[float]

    b-coefficients

  c float

    c-coefficient

  Create a new instance of CromerMannFormula for specified element.

  No return value

  atstol(stol)

    Calculate x-ray scattering factors at specified sin(theta)/lambda

    stol float or [float] | Å-1

      sin(theta)/lambda

    Return float or numpy.array.

  stollimit = 6

periodictable.cromermann.fxrayatq(symbol, Q, charge=None)

  Return x-ray scattering factors of an element at a given Q.

  symbol string

    symbol of an element or ion, e.g., “Ca”, “Ca2+”

  Q float or [float] | Å-1

    Q value

  charge int

    ion charge, overrides any valence suffixes such as “-”, “+”, “3+”.

  Return float or numpy array.

periodictable.cromermann.fxrayatstol(symbol, stol, charge=None)

  Calculate x-ray scattering factors at specified sin(theta)/lambda

  symbol string

    symbol of an element or ion, e.g., “Ca”, “Ca2+”

  stol float or [float] | Å-1

    sin(theta)/lambda

  charge int

    ion charge, overrides any valence suffixes such as “-”, “+”, “3+”.

  Return float or numpy.array.

periodictable.cromermann.getCMformula(symbol)

  Obtain Cromer-Mann formula and coefficients for a specified element.

  symbol string

    symbol of an element

  Return instance of CromerMannFormula.