[da84551] | 1 | double form_volume(double radius); |
---|
| 2 | |
---|
| 3 | double Iq(double q, double radius, double surface_dim, double cutoff_length); |
---|
| 4 | double Iqxy(double qx, double qy, double radius, double surface_dim, double cutoff_length); |
---|
| 5 | |
---|
| 6 | static double _gamln(double q) |
---|
| 7 | { |
---|
| 8 | // Lanczos approximation to the Gamma function. |
---|
| 9 | // Should be refactored out to lib/, if used elsewhere. |
---|
| 10 | double x,y,tmp,ser; |
---|
| 11 | double coeff[6]= |
---|
| 12 | {76.18009172947146, -86.50532032941677, |
---|
| 13 | 24.01409824083091, -1.231739572450155, |
---|
| 14 | 0.1208650973866179e-2,-0.5395239384953e-5}; |
---|
| 15 | int j; |
---|
| 16 | |
---|
| 17 | y=x=q; |
---|
| 18 | tmp = x+5.5; |
---|
| 19 | tmp -= (x+0.5)*log(tmp); |
---|
| 20 | ser = 1.000000000190015; |
---|
| 21 | for (j=0; j<=5; j++) { |
---|
| 22 | y+=1.0; |
---|
| 23 | ser += coeff[j]/y; |
---|
| 24 | } |
---|
| 25 | return -tmp+log(2.5066282746310005*ser/x); |
---|
| 26 | } |
---|
| 27 | |
---|
| 28 | static double surface_fractal_kernel(double q, |
---|
| 29 | double radius, |
---|
| 30 | double surface_dim, |
---|
| 31 | double cutoff_length) |
---|
| 32 | { |
---|
| 33 | double pq, sq, mmo, result; |
---|
| 34 | |
---|
| 35 | //calculate P(q) for the spherical subunits; not normalized |
---|
| 36 | pq = pow((3.0*(sin(q*radius) - q*radius*cos(q*radius))/pow((q*radius),3)),2); |
---|
| 37 | |
---|
| 38 | //calculate S(q) |
---|
| 39 | mmo = 5.0 - surface_dim; |
---|
| 40 | sq = exp(_gamln(mmo))*sin(-(mmo)*atan(q*cutoff_length)); |
---|
| 41 | sq *= pow(cutoff_length, mmo); |
---|
| 42 | sq /= pow((1.0 + (q*cutoff_length)*(q*cutoff_length)),(mmo/2.0)); |
---|
| 43 | sq /= q; |
---|
| 44 | |
---|
| 45 | //combine and return |
---|
| 46 | result = pq * sq; |
---|
| 47 | |
---|
| 48 | return result; |
---|
| 49 | } |
---|
| 50 | double form_volume(double radius){ |
---|
| 51 | |
---|
| 52 | return 1.333333333333333*M_PI*radius*radius*radius; |
---|
| 53 | } |
---|
| 54 | |
---|
| 55 | double Iq(double q, |
---|
| 56 | double radius, |
---|
| 57 | double surface_dim, |
---|
| 58 | double cutoff_length |
---|
| 59 | ) |
---|
| 60 | { |
---|
| 61 | return surface_fractal_kernel(q, radius, surface_dim, cutoff_length); |
---|
| 62 | } |
---|
| 63 | |
---|
| 64 | // Iqxy is never called since no orientation or magnetic parameters. |
---|
| 65 | double Iqxy(double qx, double qy, |
---|
| 66 | double radius, |
---|
| 67 | double surface_dim, |
---|
| 68 | double cutoff_length) |
---|
| 69 | { |
---|
| 70 | double q = sqrt(qx*qx + qy*qy); |
---|
| 71 | return surface_fractal_kernel(q, radius, surface_dim, cutoff_length); |
---|
| 72 | } |
---|
| 73 | |
---|