source: sasmodels/sasmodels/models/lamellar_stack_caille.c @ ef07e95

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Last change on this file since ef07e95 was 1c6286d, checked in by Paul Kienzle <pkienzle@…>, 7 years ago

lamellar stack/hg-stack caille: code tidying, changing loop terminator from 'i⇐N-1' to the more usual 'i<N'

  • Property mode set to 100644
File size: 1.4 KB
Line 
1/*      LamellarCaille kernel - allows for name changes of passed parameters ...
2
3*/
4
5static double
6Iq(double qval,
7   double del,
8   double fp_Nlayers,
9   double dd,
10   double Cp,
11   double sld,
12   double solvent_sld)
13{
14  int Nlayers = (int)(fp_Nlayers+0.5);    //cast to an integer for the loop
15  double contr;   //local variables of coefficient wave
16  double inten,Pq,Sq,alpha,temp,t2;
17  //double dQ, dQDefault, t1, t3;
18  // from wikipedia 0.577215664901532860606512090082402431042159335
19  const double Euler = 0.577215664901533;   // Euler's constant, increased sig figs for new models Feb 2015
20  //dQDefault = 0.0;    //[=] 1/A, q-resolution, default value
21  //dQ = dQDefault; // REMOVED UNUSED dQ calculations for new models Feb 2015
22
23  contr = sld - solvent_sld;
24
25  Pq = 2.0*contr*contr/qval/qval*(1.0-cos(qval*del));
26
27  Sq = 0.0;
28  for (int ii=1; ii < Nlayers; ii++) {
29    temp = 0.0;
30    alpha = Cp/4.0/M_PI/M_PI*(log(M_PI*ii) + Euler);
31    //t1 = 2.0*dQ*dQ*dd*dd*alpha;
32    t2 = 2.0*qval*qval*dd*dd*alpha;
33    //t3 = dQ*dQ*dd*dd*ii*ii;
34
35    temp = 1.0 - (double)ii / (double)Nlayers;
36    //temp *= cos(dd*qval*ii/(1.0+t1));
37    temp *= cos(dd*qval*ii);
38    //temp *= exp(-1.0*(t2 + t3)/(2.0*(1.0+t1)) );
39    temp *= exp(-t2/2.0);
40    //temp /= sqrt(1.0+t1);
41
42    Sq += temp;
43  }
44
45  Sq *= 2.0;
46  Sq += 1.0;
47
48  inten = 2.0*M_PI*Pq*Sq/(dd*qval*qval);
49
50  inten *= 1.0e-04;   // 1/A to 1/cm
51
52  return(inten);
53}
54
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