\(\renewcommand\AA{\text{Å}}\)
Magnetic Form Factor¶
periodictable.magnetic_ff
¶
Adds magnetic_ff[charge].t for t in j0, j2, j4, j6, and J. J should be the dipole approximation <j0> + (1  2/g) <j2>, according to the documentation for CrysFML [1] , but that does not seem to be the case in practice.
[1]  Brown. P. J. (Section 4.4.5) International Tables for Crystallography Volume C, Wilson. A. J. C.(ed). 

class
periodictable.magnetic_ff.
MagneticFormFactor
¶ Bases:
object
Magnetic form factor for the ion.
The available form factors are:
M = <j0> form factor coefficients J = <j0> + C2 <j2> form factor coeffients jn = <jn> form factor coefficients for n = 0, 2, 4, 6
Not all form factors are available for all ions. Use the expression
hasattr(ion.magnetic_ff, '<ff>')
to test for the particular form factor <ff>. The form factor coefficients are a tuple (A, a, B, b, C, c, D). The following expression computes the M/j0 and J form factors from the corresponding coefficients:s = q^2 / 16 pi^2 ff = A exp(a s^2) + B exp(b s^2) + C exp(c s^2) + D
The remaining form factors j2, j4 and j6 are scalled by an additional s^2. The form factor calculation is performed by the <ff>_Q method for <ff> in M, J, j0, j2, j4, j6. For example, here is the calculation for the M form factor for Fe^2+ computed at 0, 0.1 and 0.2:
>>> import periodictable >>> ion = periodictable.Fe.ion[2] >>> print("[%.5f, %.5f, %.5f]" ... % tuple(ion.magnetic_ff[ion.charge].M_Q([0, 0.1, 0.2]))) [1.00000, 0.99935, 0.99741]

J_Q
(Q)¶ Returns J scattering potential at Q Å^{1}

M_Q
(Q)¶ Returns j0 scattering potential at Q Å^{1}

j0_Q
(Q)¶ Returns j0 scattering potential at Q Å^{1}

j2_Q
(Q)¶ Returns j2 scattering potential at Q Å^{1}

j4_Q
(Q)¶ Returns j4 scattering potential at Q Å^{1}

j6_Q
(Q)¶ Returns j6 scattering potential at Q Å^{1}

M
¶ j0


periodictable.magnetic_ff.
formfactor_0
(j0, q)¶ Returns the scattering potential for form factor j0 at the given q.

periodictable.magnetic_ff.
formfactor_n
(jn, q)¶ Returns the scattering potential for form factor jn at the given q.

periodictable.magnetic_ff.
init
(table, reload=False)¶ Add magnetic form factor properties to the periodic table