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static double
f_constant(double q, double r, double sld)
{
const double bes = sas_3j1x_x(q * r);
const double vol = M_4PI_3 * cube(r);
return sld * vol * bes;
}
static double
outer_radius(double core_radius, double fp_n, double thickness[])
{
double r = core_radius;
int n = (int)(fp_n+0.5);
for (int i=0; i < n; i++) {
r += thickness[i];
}
return r;
}
static double
form_volume(double core_radius, double fp_n, double thickness[])
{
return M_4PI_3 * cube(outer_radius(core_radius, fp_n, thickness));
}
static double
radius_effective(int mode, double core_radius, double fp_n, double thickness[])
{
switch (mode) {
default:
case 1: // outer radius
return outer_radius(core_radius, fp_n, thickness);
case 2: // core radius
return core_radius;
}
}
static void
Fq(double q, double *F1, double *F2, double core_sld, double core_radius,
double solvent_sld, double fp_n, double sld[], double thickness[])
{
const int n = (int)(fp_n+0.5);
double f, r, last_sld;
r = core_radius;
last_sld = core_sld;
f = 0.;
for (int i=0; i<n; i++) {
f += M_4PI_3 * cube(r) * (sld[i] - last_sld) * sas_3j1x_x(q*r);
last_sld = sld[i];
r += thickness[i];
}
f += M_4PI_3 * cube(r) * (solvent_sld - last_sld) * sas_3j1x_x(q*r);
*F1 = 1e-2 * f;
*F2 = 1e-4 * f * f;
}
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