Energy Gap Code
Taylor L. Hughes
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/**************************
Code by Taylor L. Hughes June 2,2008.
to compile simply use
gcc -lm prog.c -o pp
and run pp.exe
**************************/
#include <stdio.h>
#include <math.h>
#define PI 3.1415926536
int main() {
FILE *f;
double grid=1800.0;
double t=1.0;
double div =1.0/grid;
float DD;
f = fopen ("uplot.dat", "w");// Clear out file
fclose(f);
/////////////////////////////DO Integral///////////
int inx=0; int iny=0; double sum=0.0;
for(DD=0.01;DD<10.0;DD+=0.05) {
for(inx=0;inx< (int)grid;inx++) {
for(iny=0;iny< (int)grid; iny++)
{
sum+=(2.0*PI*div)*(2.0*PI*div)/(sqrt(4.0*t*t*(cos(2.0*PI*((float)inx)*div)+cos(2.0*PI*((float)iny)*div))*(cos(2.0*PI*((float)inx)*div)+cos(2.0*PI*((float)iny)*div))+DD*DD));
}
}
sum/=((2.0*PI)*(2.0*PI));
sum/=2.0;
float out=1.0/sum;//calculate U from the integral
f = fopen ("uplot.dat", "a+");
fprintf(f,"\n%g\t %g",DD,out);
}
return 0; }
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