すみません。お手上げです。５時間以上考えたんですが、どうしても上手くいきません。
何故でしょうか?^^;。分かる方ご指摘下さい。f=1です。
http://ceram.material.tohoku.ac.jp/~takamura/class/comp16/day5/day5.html

#include <stdio.h>
#include <math.h>

main()
{

int h, k, l;
float x1=0.0, x2=0.0, x3=0.5, x4=0.5, y1=0.0, y2=0.5, y3=0.5, y4=0.0, z1=0.0, z2=0.5, z3=0.0, z4=0.5;
double a, d, lambda, theta, F, FF, Fa, Fb;

a = 0.3615;
lambda = 0.154056;

for( h = -4; h<=4; h++){
for( k = -4; k<=4; k++){
for( l = -4; l<=4; l++){
if ( !(h==0 && k==0 && l==0) ){

d = a / sqrt(h*h+k*k+l*l);
theta = 2*asin(lambda/(2*d));
if ( F > 0.001){
Fa = 1+cos(6.28*(h*x2+k*y2+l*z2))+cos(6.28*(h*x3+k*y3+l*z3))+cos(6.28*(h*x4+k*y4+l*z4));
Fb = sin(6.28*(h*x1+k*y1+l*z1))+sin(6.28*(h*x2+k*y2+l*z2))+sin(6.28*(h*x3+k*y3+l*z3))+sin(6.28*(h*x4+k*y4+l*z4));

FF = Fa*Fa + Fb*Fb

printf("( %2d %2d %2d ) d = %.4lf 2theta = %.41fnm F_square = %.41f\n", h, k, l, d, theta, FF);
}}}}}}