polybash

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<math.h>
#define PI 3.1415926

//modified modified
struct atom{
	double x,y,z;
};

int n_atom;
double xlo,xhi,ylo,yhi,zlo,zhi,step_length;
struct atom a[1000];

int write_head(FILE *fp)
{
	fprintf(fp,"#LAMMPS single-chain polymer data file\n\n");
	fprintf(fp,"%12d  atoms\n",n_atom);
	fprintf(fp,"%12d  bonds\n\n",n_atom-1);
	fprintf(fp,"%12d  atom types\n",1);
	fprintf(fp,"%12d  bond types\n\n",1);
	fprintf(fp,"%-10f  %-10f  xlo xhi\n",xlo,xhi);
	fprintf(fp,"%-10f  %-10f  ylo yhi\n",ylo,yhi);
	fprintf(fp,"%-10f  %-10f  zlo zhi\n\n",zlo,zhi);
	fprintf(fp,"Masses\n\n");
	fprintf(fp,"%12d  %.6f\n\n",1,1.000000);
	return 0;
}

int write_atoms(FILE *fp)
{
	int i;
	double theta,fi;
	srand(time(0));
	a[0].x=rand()/(RAND_MAX+1.0)*(xhi-xlo)+xlo;
	a[0].y=rand()/(RAND_MAX+1.0)*(yhi-ylo)+ylo;
	a[0].z=rand()/(RAND_MAX+1.0)*(zhi-zlo)+zlo;
	fprintf(fp,"Atoms\n\n");
	for(i=1;i<n_atom;i++){
		do{
			theta=PI*rand()/(RAND_MAX+1.0);
			fi=2*PI*rand()/(RAND_MAX+1.0);
			a[i].x=a[i-1].x+step_length*sin(theta)*cos(fi);
			a[i].y=a[i-1].y+step_length*sin(theta)*sin(fi);
			a[i].z=a[i-1].z+step_length*cos(theta);
		}while(a[i].x<xlo || a[i].x>xhi ||a[i].y<ylo||a[i].y>yhi||a[i].z<zlo||a[i].z>zhi);
	}
	for(i=0;i<n_atom;i++){
		fprintf(fp,"%8d%8d%8d%10.3f%10.3f%10.3f\n",i+1,1,1,a[i].x,a[i].y,a[i].z);
	}
	fprintf(fp,"\n");
	return 0;
}

int write_bonds(FILE *fp)
{
	int i;
	fprintf(fp,"Bonds\n\n");
	for(i=0;i<n_atom-1;i++)
	{
		fprintf(fp,"%8d%8d%8d%8d\n",i+1,1,i+1,i+2);
	}
	return 0;
}

int main(int argc,char* argv[])
{
	FILE *fp1=fopen("data.poly","w");
	n_atom=atoi(argv[1]);
	xlo=atof(argv[2]);
	xhi=atof(argv[3]);
	ylo=atof(argv[4]);
	yhi=atof(argv[5]);
	zlo=atof(argv[6]);
	zhi=atof(argv[7]);
	step_length=atof(argv[8]);
	write_head(fp1);
	write_atoms(fp1);
	write_bonds(fp1);
	fclose(fp1);
	return 0;
}