RPA models


Calculates the macroscopic scattering intensity for a multi-component homogeneous mixture of polymers using the Random Phase Approximation. This general formalism contains 10 specific cases

Case 0: C/D binary mixture of homopolymers

Case 1: C-D diblock copolymer

Case 2: B/C/D ternary mixture of homopolymers

Case 3: C/C-D mixture of a homopolymer B and a diblock copolymer C-D

Case 4: B-C-D triblock copolymer

Case 5: A/B/C/D quaternary mixture of homopolymers

Case 6: A/B/C-D mixture of two homopolymers A/B and a diblock C-D

Case 7: A/B-C-D mixture of a homopolymer A and a triblock B-C-D

Case 8: A-B/C-D mixture of two diblock copolymers A-B and C-D

Case 9: A-B-C-D tetra-block copolymer

**NB: these case numbers are different from those in the NIST SANS package!**

Only one case can be used at any one time.

The RPA (mean field) formalism only applies only when the multicomponent polymer mixture is in the homogeneous mixed-phase region.

**Component D is assumed to be the "background" component (ie, all contrasts are calculated with respect to component D).** So the scattering contrast for a C/D blend = [SLD(component C) - SLD(component D)]$^2$.

Depending on which case is being used, the number of fitting parameters - the segment lengths (ba, bb, etc) and $\chi$ parameters (Kab, Kac, etc) - vary. The *scale* parameter should be held equal to unity.

The input parameters are the degrees of polymerization, the volume fractions, the specific volumes, and the neutron scattering length densities for each component.


A Z Akcasu, R Klein and B Hammouda, *Macromolecules*, 26 (1993) 4136

Example Data:


Created By butler
Uploaded Sept. 15, 2016, 5:27 p.m.
Category Shape-Independent
Score 0
Verified This model has not been verified by a member of the SasView team
In Library This model is not currently included in the SasView library. You must download the files and install it yourself.
Files rpa.py


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