# core_multi_shell

This model provides the scattering from a spherical core with 1 to 4 concentric shell structures. The SLDs of the core and each shell are individually specified.

Parameter Description Units Default value
scale Source intensity None 1
background Source background cm-1 0.001
sld_core Core scattering length density 10-6-2 1
sld_solvent Solvent scattering length density 10-6-2 6.4
n number of shells None 1
sld[n] scattering length density of shell k 10-6-2 1.7
thickness[n] Thickness of shell k 40

The returned value is scaled to units of cm-1 sr-1, absolute scale.

Definition

This model is a trivial extension of the CoreShell function to a larger number of shells. The scattering length density profile for the default sld values (w/ 4 shells).

The 2D scattering intensity is the same as $$P(q)$$ above, regardless of the orientation of the $$\vec q$$ vector which is defined as

$q = \sqrt{q_x^2 + q_y^2}$

Note

Be careful! The SLDs and scale can be highly correlated. Hold as many of these parameters fixed as possible.

Note

The outer most radius (= radius + thickness) is used as the effective radius for $$S(Q)$$ when $$P(Q)*S(Q)$$ is applied.

For information about polarised and magnetic scattering, see the Polarisation/Magnetic Scattering documentation.

Our model uses the form factor calculations implemented in a c-library provided by the NIST Center for Neutron Research (Kline, 2006) [2].

References

 [1] See the core_shell_sphere model documentation.
 [2] S R Kline, J Appl. Cryst., 39 (2006) 895
 [3] L A Feigin and D I Svergun, Structure Analysis by Small-Angle X-Ray and Neutron Scattering, Plenum Press, New York, 1987.

Authorship and Verification

• Author: NIST IGOR/DANSE Date: pre 2010