From: hackbard <hackbard@sage.physik.uni-augsburg.de>
Date: Sun, 17 Feb 2008 18:16:52 +0000 (+0100)
Subject: added normalization to pair correlation calc
X-Git-Url: https://hackdaworld.org/gitweb/?a=commitdiff_plain;h=4d1515cac0af6b11df3d34a0bb19ea885676ee73;p=physik%2Fposic.git

added normalization to pair correlation calc
---

diff --git a/moldyn.c b/moldyn.c
index 93c72da..f2923c3 100644
--- a/moldyn.c
+++ b/moldyn.c
@@ -2375,13 +2375,13 @@ int calculate_pair_correlation(t_moldyn *moldyn,double dr,void *ptr) {
 	unsigned char bc;
 	t_3dvec dist;
 	double d;
-	//double norm;
+	double norm;
 	int o,s;
 	unsigned char ibrand;
 
 	lc=&(moldyn->lc);
 
-	slots=moldyn->cutoff/dr;
+	slots=2.0*moldyn->cutoff/dr;
 	o=2*slots;
 
 	if(slots*dr<=moldyn->cutoff)
@@ -2458,7 +2458,7 @@ int calculate_pair_correlation(t_moldyn *moldyn,double dr,void *ptr) {
 				d=v3_absolute_square(&dist);
 
 				/* ignore if greater or equal cutoff */
-				if(d>=moldyn->cutoff_square)
+				if(d>=4.0*moldyn->cutoff_square)
 					continue;
 
 				/* fill the slots */
@@ -2494,16 +2494,17 @@ int calculate_pair_correlation(t_moldyn *moldyn,double dr,void *ptr) {
 		}
 	}
 
-	/* normalization 
+	/* normalization */
 	for(i=1;i<slots;i++) {
-		 // normalization: 4 pi r r dr
+		 // normalization: 4 pi r^2 dr
 		 // here: not double counting pairs -> 2 pi r r dr
-		norm=2*M_PI*moldyn->count*(i*dr*i*dr)*dr;
+		 // ... and actually it's a constant times r^2
+		norm=i*i*dr*dr;
 		stat[i]/=norm;
 		stat[slots+i]/=norm;
 		stat[o+i]/=norm;
 	}
-	*/
+	/* */
 
 	if(ptr==NULL) {
 		/* todo: store/print pair correlation function */
diff --git a/pair_corr_calc_script b/pair_corr_calc_script
index f2c64ec..7f25a74 100755
--- a/pair_corr_calc_script
+++ b/pair_corr_calc_script
@@ -39,11 +39,12 @@ set ytic auto
 set title 'Pair correlation function' 
 set xlabel 'r [A]' 
 set ylabel 'g(r) [a.u.]' 
+unset ytics
 set terminal postscript eps enhanced color solid lw 1 'Helvetica' 14 
 set output '$pdir/pair_corr.eps' 
 EOF
 
-echo -en "plot [1.5:3.0] " >> $pfile
+echo -en "plot [1.5:6.0] " >> $pfile
 
 komma=0
 
diff --git a/pair_correlation_calc.c b/pair_correlation_calc.c
index f04c4e4..e5903aa 100644
--- a/pair_correlation_calc.c
+++ b/pair_correlation_calc.c
@@ -52,7 +52,7 @@ int main(int argc,char **argv) {
 	//moldyn.cutoff_square*=4;
 
 	dr=atof(argv[2]);
-	slots=moldyn.cutoff/dr;
+	slots=2.0*moldyn.cutoff/dr;
 	printf("[pair corr calc]\n");
 	printf("  slots: %d\n",slots);
 	printf("  cutoff: %f\n",moldyn.cutoff);