1 | double form_volume(double length_a, double b2a_ratio, double c2a_ratio); |
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2 | double Iq(double q, double sld, double solvent_sld, double length_a, |
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3 | double b2a_ratio, double c2a_ratio); |
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4 | |
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5 | double form_volume(double length_a, double b2a_ratio, double c2a_ratio) |
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6 | { |
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7 | return length_a * (length_a*b2a_ratio) * (length_a*c2a_ratio); |
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8 | } |
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9 | |
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10 | double Iq(double q, |
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11 | double sld, |
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12 | double solvent_sld, |
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13 | double length_a, |
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14 | double b2a_ratio, |
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15 | double c2a_ratio) |
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16 | { |
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17 | const double length_b = length_a * b2a_ratio; |
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18 | const double length_c = length_a * c2a_ratio; |
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19 | const double a_half = 0.5 * length_a; |
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20 | const double b_half = 0.5 * length_b; |
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21 | const double c_half = 0.5 * length_c; |
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22 | |
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23 | //Integration limits to use in Gaussian quadrature |
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24 | const double v1a = 0.0; |
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25 | const double v1b = M_PI_2; //theta integration limits |
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26 | const double v2a = 0.0; |
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27 | const double v2b = M_PI_2; //phi integration limits |
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28 | |
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29 | double outer_sum = 0.0; |
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30 | for(int i=0; i<GAUSS_N; i++) { |
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31 | const double theta = 0.5 * ( GAUSS_Z[i]*(v1b-v1a) + v1a + v1b ); |
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32 | double sin_theta, cos_theta; |
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33 | SINCOS(theta, sin_theta, cos_theta); |
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34 | |
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35 | const double termC = sas_sinx_x(q * c_half * cos_theta); |
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36 | |
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37 | double inner_sum = 0.0; |
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38 | for(int j=0; j<GAUSS_N; j++) { |
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39 | double phi = 0.5 * ( GAUSS_Z[j]*(v2b-v2a) + v2a + v2b ); |
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40 | double sin_phi, cos_phi; |
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41 | SINCOS(phi, sin_phi, cos_phi); |
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42 | |
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43 | // Amplitude AP from eqn. (12), rewritten to avoid round-off effects when arg=0 |
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44 | const double termA = sas_sinx_x(q * a_half * sin_theta * sin_phi); |
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45 | const double termB = sas_sinx_x(q * b_half * sin_theta * cos_phi); |
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46 | const double AP = termA * termB * termC; |
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47 | inner_sum += GAUSS_W[j] * AP * AP; |
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48 | } |
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49 | inner_sum = 0.5 * (v2b-v2a) * inner_sum; |
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50 | outer_sum += GAUSS_W[i] * inner_sum * sin_theta; |
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51 | } |
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52 | |
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53 | double answer = 0.5*(v1b-v1a)*outer_sum; |
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54 | |
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55 | // Normalize by Pi (Eqn. 16). |
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56 | // The term (ABC)^2 does not appear because it was introduced before on |
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57 | // the definitions of termA, termB, termC. |
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58 | // The factor 2 appears because the theta integral has been defined between |
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59 | // 0 and pi/2, instead of 0 to pi. |
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60 | answer /= M_PI_2; //Form factor P(q) |
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61 | |
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62 | // Multiply by contrast^2 and volume^2 |
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63 | const double volume = length_a * length_b * length_c; |
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64 | answer *= square((sld-solvent_sld)*volume); |
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65 | |
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66 | // Convert from [1e-12 A-1] to [cm-1] |
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67 | answer *= 1.0e-4; |
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68 | |
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69 | return answer; |
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70 | } |
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71 | |
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72 | |
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73 | double Iqabc(double qa, double qb, double qc, |
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74 | double sld, |
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75 | double solvent_sld, |
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76 | double length_a, |
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77 | double b2a_ratio, |
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78 | double c2a_ratio) |
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79 | { |
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80 | const double length_b = length_a * b2a_ratio; |
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81 | const double length_c = length_a * c2a_ratio; |
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82 | const double a_half = 0.5 * length_a; |
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83 | const double b_half = 0.5 * length_b; |
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84 | const double c_half = 0.5 * length_c; |
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85 | const double volume = length_a * length_b * length_c; |
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86 | |
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87 | // Amplitude AP from eqn. (13) |
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88 | |
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89 | const double termA = sas_sinx_x(qa * a_half); |
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90 | const double termB = sas_sinx_x(qb * b_half); |
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91 | const double termC = sas_sinx_x(qc * c_half); |
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92 | |
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93 | const double AP = termA * termB * termC; |
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94 | |
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95 | // Multiply by contrast^2. Factor corresponding to volume^2 cancels with previous normalization. |
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96 | const double delrho = sld - solvent_sld; |
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97 | |
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98 | // Convert from [1e-12 A-1] to [cm-1] |
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99 | return 1.0e-4 * square(volume * delrho * AP); |
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100 | } |
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