1 files changed, 164 insertions, 0 deletions
diff --git a/src/sfac.c b/src/sfac.c
new file mode 100644
index 00000000..4c3dabd3
--- /dev/null
+++ b/src/sfac.c
@@ -0,0 +1,164 @@
+/*
+ * 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;
+}