bethe_lattice Subroutine

subroutine bethe_lattice(dos,ome,Lk,D)
  real(8)          :: dos(Lk),ome(Lk)
  integer          :: Lk
  real(8),optional :: D
  integer          :: ie
  real(8)          :: de,e,D_
  complex(8)       :: gf,zeta
  D_=1.d0;if(present(D))D_=D
  de= 2.d0*D/dble(Lk-1)
  write(*,"(A,I8,A)")"Bethe Lattice with:",Lk," e-points"
  open(10,file="DOSbethe.lattice")
  do ie=1,Lk
     e=-D_ + dble(ie-1)*de
     dos(ie)=dens_bethe(e,D_)*de
     ome(ie)=e
     write(10,*)e,dos(ie)/de
  enddo
  close(10)
end subroutine bethe_lattice