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/*
* sfac.c
*
* Scattering factors
*
* (c) 2007-2009 Thomas White <thomas.white@desy.de>
*
* pattern_sim - Simulate diffraction patterns from small crystals
*
*/
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include <complex.h>
#include <string.h>
#include "utils.h"
#include "sfac.h"
/* Look up f1 and f2 for this atom at this energy (in J/photon) */
static double complex get_f1f2(const char *n, double en)
{
FILE *fh;
char filename[64];
char line[1024];
char *rval;
double last_E, last_f1, last_f2;
snprintf(filename, 63, "scattering-factors/%s.nff", n);
fh = fopen(filename, "r");
if ( fh == NULL ) {
fprintf(stderr, "Couldn't open file '%s'\n", filename);
return 0.0;
}
en = J_to_eV(en);
/* Discard first line */
fgets(line, 1023, fh);
last_E = 0.0;
last_f1 = 0.0;
last_f2 = 0.0;
do {
int r;
double E, f1, f2;
float E_f, f1_f, f2_f;
rval = fgets(line, 1023, fh);
r = sscanf(line, "%f %f %f", &E_f, &f1_f, &f2_f);
if ( r != 3 ) {
fprintf(stderr, "WTF?\n");
abort();
}
/* Promote to double precision */
E = E_f; f1 = f1_f; f2 = f2_f;
/* Find the first energy greater than the required value */
if ( E < en ) {
/* Store old values ready for interpolation*/
last_E = E;
last_f1 = f1;
last_f2 = f2;
} else {
/* Perform (linear) interpolation */
double f;
double actual_f1, actual_f2;
f = (en - last_E) / (E - last_E);
actual_f1 = last_f1 + f * (f1 - last_f1);
actual_f2 = last_f2 + f * (f2 - last_f2);
fclose(fh);
return actual_f1 + I*actual_f2;
}
} while ( rval != NULL );
fclose(fh);
fprintf(stderr, "Couldn't find scattering factors for '%s' at %f eV!\n",
n, en);
return 0.0;
}
/* s = sin(theta)/lambda */
static double get_waas_kirf(const char *n, double s)
{
FILE *fh;
char *rval;
double f;
float a1, a2, a3, a4, a5, c, b1, b2, b3, b4, b5;
double s2;
fh = fopen("scattering-factors/f0_WaasKirf.dat", "r");
if ( fh == NULL ) {
fprintf(stderr, "Couldn't open f0_WaasKirf.dat\n");
return 0.0;
}
do {
int r;
char line[1024];
char sp[1024];
int Z;
rval = fgets(line, 1023, fh);
if ( (line[0] != '#') || (line[1] != 'S') ) continue;
r = sscanf(line, "#S %i %s", &Z, sp);
if ( (r != 2) || (strcmp(sp, n) != 0) ) continue;
/* Skip two lines */
fgets(line, 1023, fh);
fgets(line, 1023, fh);
/* Read scattering coefficients */
rval = fgets(line, 1023, fh);
r = sscanf(line, " %f %f %f %f %f %f %f %f %f %f %f",
&a1, &a2, &a3, &a4, &a5, &c, &b1, &b2, &b3, &b4, &b5);
if ( r != 11 ) {
fprintf(stderr, "Couldn't read scattering factors\n");
return 0.0;
}
break;
} while ( rval != NULL );
fclose(fh);
s2 = pow(s/1e10, 2.0); /* s2 is s squared in Angstroms squared */
f = c + a1*exp(-b1*s2) + a2*exp(-b2*s2) + a3*exp(-b3*s2)
+ a4*exp(-b4*s2) + a5*exp(-b5*s2);
return f;
}
/* Get complex scattering factors for element 'n' at energy 'en' (J/photon),
* at resolution 's' = sin(theta)/lambda (in m^-1) */
double complex get_sfac(const char *n, double s, double en)
{
double complex f1f2;
double fq, fq0;
f1f2 = get_f1f2(n, en);
fq = get_waas_kirf(n, s);
fq0 = get_waas_kirf(n, 0.0);
return fq - fq0 + f1f2;
}
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