source: sasmodels/sasmodels/models/fractal.c @ 46ed760

core_shell_microgelscostrafo411magnetic_modelrelease_v0.94release_v0.95ticket-1257-vesicle-productticket_1156ticket_1265_superballticket_822_more_unit_tests
Last change on this file since 46ed760 was 12dbc90, checked in by butler, 8 years ago

fractal model converted and docs checked
  • Property mode set to 100644
File size: 2.2 KB
Line 
1double form_volume(double radius);
2
3double Iq(double q,
4          double volfraction,
5          double radius,
6          double fractal_dim,
7          double cor_length,
8          double sld_block,
9          double sld_solvent);
10
11double Iqxy(double qx, double qy,
12          double volfraction,
13          double radius,
14          double fractal_dim,
15          double cor_length,
16          double sld_block,
17          double sld_solvent);
18
19
20double Iq(double q,
21          double volfraction,
22          double radius,
23          double fractal_dim,
24          double cor_length,
25          double sld_block,
26          double sld_solvent)
27{
28    double qr,r0,Df,corr,phi,sldp,sldm;
29    double pq,sq,inten;
30   
31     // Actively check the argument - needed for mass fractal - is it needie
32     //here?
33    if (fractal_dim <= 0.0){
34       return 0.0;
35    }
36   
37    phi = volfraction;        // volume fraction of building block spheres...
38    r0 = radius;     //  radius of building block
39    Df = fractal_dim;     //  fractal dimension
40    corr = cor_length;       //  correlation length of fractal-like aggregates
41    sldp = sld_block;       // SLD of building block
42    sldm = sld_solvent;       // SLD of matrix or solution
43 
44     qr=q*r0;
45   
46    //calculate P(q) for the spherical subunits
47    pq = phi*M_4PI_3*r0*r0*r0*(sldp-sldm)*(sldp-sldm)*sph_j1c(qr)*sph_j1c(qr);
48   
49    //calculate S(q)
50    sq = Df*sas_gamma(Df-1.0)*sin((Df-1.0)*atan(q*corr));
51    sq /= pow(qr,Df) * pow((1.0 + 1.0/(q*corr)/(q*corr)),((Df-1.0)/2.0));
52    sq += 1.0;
53   
54    //combine, scale to units cm-1 sr-1 (assuming data on absolute scale)
55    //and return
56    inten = pq*sq;
57    // convert I(1/A) to (1/cm)
58    inten *= 1.0e8;
59    //convert rho^2 in 10^-6 1/A to 1/A
60    inten *= 1.0e-12;   
61   
62   
63    return(inten);
64}
65
66
67// Iqxy is never called since no orientation or magnetic parameters.
68double Iqxy(double qx, double qy,
69          double volfraction,
70          double radius,
71          double fractal_dim,
72          double cor_length,
73          double sld_block,
74          double sld_solvent)
75{
76    double q = sqrt(qx*qx + qy*qy);
77    return Iq(q,
78        volfraction, radius,
79        fractal_dim, cor_length,
80        sld_block, sld_solvent);
81
82}
83
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