source: sasmodels/sasmodels/models/hollow_rectangular_prism.c @ ab2aea8

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Last change on this file since ab2aea8 was ab2aea8, checked in by Paul Kienzle <pkienzle@…>, 7 years ago

code cleanup for rectangular prism models

  • Property mode set to 100644
File size: 3.0 KB
Line 
1double form_volume(double length_a, double b2a_ratio, double c2a_ratio, double thickness);
2double Iq(double q, double sld, double solvent_sld, double length_a, 
3          double b2a_ratio, double c2a_ratio, double thickness);
4
5double form_volume(double length_a, double b2a_ratio, double c2a_ratio, double thickness)
6{
7    double length_b = length_a * b2a_ratio;
8    double length_c = length_a * c2a_ratio;
9    double a_core = length_a - 2.0*thickness;
10    double b_core = length_b - 2.0*thickness;
11    double c_core = length_c - 2.0*thickness;
12    double vol_core = a_core * b_core * c_core;
13    double vol_total = length_a * length_b * length_c;
14    double vol_shell = vol_total - vol_core;
15    return vol_shell;
16}
17
18double Iq(double q,
19    double sld,
20    double solvent_sld,
21    double length_a,
22    double b2a_ratio,
23    double c2a_ratio,
24    double thickness)
25{
26    double termA1, termA2, termB1, termB2, termC1, termC2;
27   
28    double length_b = length_a * b2a_ratio;
29    double length_c = length_a * c2a_ratio;
30    double a_half = 0.5 * length_a;
31    double b_half = 0.5 * length_b;
32    double c_half = 0.5 * length_c;
33    double vol_total = length_a * length_b * length_c;
34    double vol_core = 8.0 * (a_half-thickness) * (b_half-thickness) * (c_half-thickness);
35
36    //Integration limits to use in Gaussian quadrature
37    double v1a = 0.0;
38    double v1b = M_PI_2;  //theta integration limits
39    double v2a = 0.0;
40    double v2b = M_PI_2;  //phi integration limits
41   
42    double outer_sum = 0.0;
43   
44    for(int i=0; i<76; i++) {
45
46        double theta = 0.5 * ( Gauss76Z[i]*(v1b-v1a) + v1a + v1b );   
47
48        double termC1 = sinc(q * c_half * cos(theta));
49        double termC2 = sinc(q * (c_half-thickness)*cos(theta));
50
51        double inner_sum = 0.0;
52       
53        for(int j=0; j<76; j++) {
54
55            double phi = 0.5 * ( Gauss76Z[j]*(v2b-v2a) + v2a + v2b ); 
56
57            // Amplitude AP from eqn. (13), rewritten to avoid round-off effects when arg=0
58
59            termA1 = sinc(q * a_half * sin(theta) * sin(phi));
60            termA2 = sinc(q * (a_half-thickness) * sin(theta) * sin(phi));
61
62            termB1 = sinc(q * b_half * sin(theta) * cos(phi));
63            termB2 = sinc(q * (b_half-thickness) * sin(theta) * cos(phi));
64
65            double AP1 = vol_total * termA1 * termB1 * termC1;
66            double AP2 = vol_core * termA2 * termB2 * termC2;
67
68            inner_sum += Gauss76Wt[j] * square(AP1-AP2);
69
70        }
71
72        inner_sum = 0.5 * (v2b-v2a) * inner_sum;
73        outer_sum += Gauss76Wt[i] * inner_sum * sin(theta);
74
75    }
76
77    double answer = 0.5*(v1b-v1a)*outer_sum;
78
79    // Normalize as in Eqn. (15) without the volume factor (as cancels with (V*DelRho)^2 normalization)
80    // The factor 2 is due to the different theta integration limit (pi/2 instead of pi)
81    answer /= M_PI_2;
82
83    // Multiply by contrast^2. Factor corresponding to volume^2 cancels with previous normalization.
84    answer *= square(sld-solvent_sld);
85
86    // Convert from [1e-12 A-1] to [cm-1]
87    answer *= 1.0e-4;
88
89    return answer;
90   
91}
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