PROGRAM fcclattice

IMPLICIT NONE

REAL, DIMENSION(1000,3) :: atoms ! list of atomic coordinates
REAL, DIMENSION(4,3) :: pcell ! atoms in primitive unit cell
REAL, PARAMETER :: lc = 3.62 ! lattice constant in ang

INTEGER :: i, j, k, m, n
INTEGER, PARAMETER :: xcell=3, ycell=3, zcell=3 ! number of cells




! first atom in primitive unit cell
pcell(1,1) = 0.0
pcell(1,2) = 0.0
pcell(1,3) = 0.0
! second atom in primitive unit cell
pcell(2,1) = 0.5
pcell(2,2) = 0.5
pcell(2,3) = 0.0
! third atom in primitive unit cell
pcell(3,1) = 0.5
pcell(3,2) = 0.0
pcell(3,3) = 0.5
! fourth atom in primitive unit cell
pcell(4,1) = 0.0
pcell(4,2) = 0.5
pcell(4,3) = 0.5

m=0 ! atoms position

DO i = 0, xcell
   DO j = 0, ycell
     DO k = 0, zcell
        DO n = 1, 4
           m = m+1 ! next atom position
           atoms(m,1) = (pcell(n,1) + i)*lc 
           atoms(m,2) = (pcell(n,2) + j)*lc
           atoms(m,3) = (pcell(n,3) + k)*lc
        END DO
     END DO
  END DO
END DO

! Print xyz file to stdout

! number of atoms
print *, m
! comment
print *, '4x4x4 FCC Cu lattice'
! atoms
do i = 1, m
   print '(A,F10.5,F10.5,F10.5,I10)', 'Cu', atoms(i,:),i
end do


END PROGRAM fcclattice