Changeset 20c856a in sasmodels


Ignore:
Timestamp:
Mar 7, 2017 1:19:23 AM (8 years ago)
Author:
butler
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
Added
Removed

  • sasmodels/models/rpa.c

    racfb094 r20c856a  
    309309 
    310310  //calculate contrast where L[i] is the scattering length of i and D is the matrix 
    311   //need to verify why the sqrt of Nav rather than just Nav (assuming v is molar volume) 
     311  //Note that should multiply by Nav to get units of SLD which will become 
     312  // Nav*2 in the next line (SLD^2) but then normalization in that line would 
     313  //need to divide by Nav leaving only Nav or sqrt(Nav) before squaring.  
    312314  Nav=6.022045e+23; 
    313315  Lad=(L[0]/v[0]-L[3]/v[3])*sqrt(Nav); 
    … …  
    317319  Intg=Lad*Lad*S11+Lbd*Lbd*S22+Lcd*Lcd*S33+2.0*Lad*Lbd*S12+2.0*Lbd*Lcd*S23+2.0*Lad*Lcd*S13; 
    318320 
    319   //rescale for units of Lij^2 (in 10e-12 m^2 to m^2 ?) 
    320   Intg *= 1.0e-24;     
     321  //rescale for units of Lij^2 (fm^2 to cm^2) 
     322  Intg *= 1.0e-26;     
    321323 
    322324  return Intg; 

  • sasmodels/models/rpa.py

    rbb73096 r20c856a  
    11r""" 
     2Definition 
     3---------- 
     4 
    25Calculates the macroscopic scattering intensity for a multi-component 
    36homogeneous mixture of polymers using the Random Phase Approximation. 
    … …  
    2427Case 9: A-B-C-D tetra-block copolymer 
    2528 
    26 **NB: these case numbers are different from those in the NIST SANS package!** 
     29.. note:: 
     30    These case numbers are different from those in the NIST SANS package! 
    2731 
    28 Only one case can be used at any one time. 
     32USAGE NOTES: 
    2933 
    30 The RPA (mean field) formalism only applies only when the multicomponent 
    31 polymer mixture is in the homogeneous mixed-phase region. 
    32  
    33 **Component D is assumed to be the "background" component (ie, all contrasts 
    34 are calculated with respect to component D).** So the scattering contrast 
    35 for a C/D blend = [SLD(component C) - SLD(component D)]\ :sup:`2`. 
    36  
    37 Depending on which case is being used, the number of fitting parameters - the 
    38 segment lengths (ba, bb, etc) and $\chi$ parameters (Kab, Kac, etc) - vary. 
    39 The *scale* parameter should be held equal to unity. 
    40  
    41 The input parameters are the degrees of polymerization, the volume fractions, 
    42 the specific volumes, and the neutron scattering length densities for each 
    43 component. 
     34* Only one case can be used at any one time. 
     35* The RPA (mean field) formalism only applies only when the multicomponent 
     36  polymer mixture is in the homogeneous mixed-phase region. 
     37* **Component D is assumed to be the "background" component (ie, all contrasts 
     38  are calculated with respect to component D).** So the scattering contrast 
     39  for a C/D blend = [SLD(component C) - SLD(component D)]\ :sup:`2`. 
     40* Depending on which case is being used, the number of fitting parameters can  
     41  vary.  Note that in general the degrees of polymerization, the volume 
     42  fractions, the molar volumes, and the neutron scattering lengths for each 
     43  component are obtained from other methods and held fixed while the segment 
     44  lengths (b\ :sub:`a`, b\ :sub:`b`, etc) and $\chi$ parameters (K\ :sub:`ab`, 
     45  K\ :sub:`ac`, etc). The *scale* parameter should be held equal to unity. 
    4446 
    4547 
    … …  
    4749---------- 
    4850 
    49 A Z Akcasu, R Klein and B Hammouda, *Macromolecules*, 26 (1993) 4136 
     51.. [#] A Z Akcasu, R Klein and B Hammouda, *Macromolecules*, 26 (1993) 4136 
    5052""" 
    5153 
    … …  
    5355 
    5456name = "rpa" 
    55 title = "Random Phase Approximation - unfinished work in progress" 
     57title = "Random Phase Approximation" 
    5658description = """ 
    5759This formalism applies to multicomponent polymer mixtures in the 
    … …  
    9092    ["N[4]", "", 1000.0, [1, inf], "", "Degree of polymerization"], 
    9193    ["Phi[4]", "", 0.25, [0, 1], "", "volume fraction"], 
    92     ["v[4]", "mL/mol", 100.0, [0, inf], "", "specific volume"], 
     94    ["v[4]", "mL/mol", 100.0, [0, inf], "", "molar volume"], 
    9395    ["L[4]", "fm", 10.0, [-inf, inf], "", "scattering length"], 
    9496    ["b[4]", "Ang", 5.0, [0, inf], "", "segment length"], 
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