# Changeset 20c856a in sasmodels

Ignore:
Timestamp:
Mar 7, 2017 1:19:23 AM (2 years ago)
Branches:
master, core_shell_microgels, costrafo411, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
Children:
9ae85f0, 3a45c2c
Parents:
f4b36fa
Message:

Final rpa model corrections (correct scale and units) and verified with
one of original authors on paper. Fixes #593.

while documentation was updated minimally to be usable it could use more
thorough work as can many which is the subject of other tickets. Also
annoying is that the example plot is useless. It is however
autogenerated from "default parameters" which is not helpful in this
particular case. Will submit new ticket for that.

Location:
sasmodels/models
Files:
2 edited

### Legend:

Unmodified
 rbb73096 r""" Definition ---------- Calculates the macroscopic scattering intensity for a multi-component homogeneous mixture of polymers using the Random Phase Approximation. Case 9: A-B-C-D tetra-block copolymer **NB: these case numbers are different from those in the NIST SANS package!** .. note:: These case numbers are different from those in the NIST SANS package! Only one case can be used at any one time. USAGE NOTES: 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)]\ :sup: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. * 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)]\ :sup:2. * Depending on which case is being used, the number of fitting parameters can vary.  Note that in general the degrees of polymerization, the volume fractions, the molar volumes, and the neutron scattering lengths for each component are obtained from other methods and held fixed while the segment lengths (b\ :sub:a, b\ :sub:b, etc) and $\chi$ parameters (K\ :sub:ab, K\ :sub:ac, etc). The *scale* parameter should be held equal to unity. ---------- A Z Akcasu, R Klein and B Hammouda, *Macromolecules*, 26 (1993) 4136 .. [#] A Z Akcasu, R Klein and B Hammouda, *Macromolecules*, 26 (1993) 4136 """ name = "rpa" title = "Random Phase Approximation - unfinished work in progress" title = "Random Phase Approximation" description = """ This formalism applies to multicomponent polymer mixtures in the ["N[4]", "", 1000.0, [1, inf], "", "Degree of polymerization"], ["Phi[4]", "", 0.25, [0, 1], "", "volume fraction"], ["v[4]", "mL/mol", 100.0, [0, inf], "", "specific volume"], ["v[4]", "mL/mol", 100.0, [0, inf], "", "molar volume"], ["L[4]", "fm", 10.0, [-inf, inf], "", "scattering length"], ["b[4]", "Ang", 5.0, [0, inf], "", "segment length"],