anchor.diff:         integer atom1_id,atom2_id
          integer k 
          logical ok
  +       logical osmooth
          double precision f
          integer fn_in
          integer fn_out
  
positive.code:        atom2_tag = " "
         rmax = -1
         nb = -1
  c
  c      ------------------------
  c      allocate io file array
  
negative.code:        end do
  c       
  c      average RDF over the frames
         if(overb) 
       +   write(*,*) "averaging over ",naver," smaples"
         gr = gr/real(naver)
  c
  c      smoothing g(r) per Allan/Tild. p 204 (6.48)
  c      ------------------------------------------
         if(osmooth) then
         if(overb) 
       +   write(*,*) "smoothing rdf"
         gr0=0.0d0
         gr0(1)=(69.0*gr(1)+4.0*gr(2)-6.0*gr(3)+
       >         4.0*gr(4)-gr(5))/70.0d0
         gr0(2)=(2.0*gr(1)+27.0*gr(2)+12.0*gr(3)
       >  -8.0*gr(4)+2.0*gr(5))/35.0d0
         do i=3,nb-2
           gr0(i) =(-3.0*gr(i-2)+12.0*gr(i-1)+17.0*gr(i)+
       >            12.0*gr(i+1)-3.0*gr(i+2))/35.0d0 
         end do
         gr0(nb-1)=(2.0*gr(nb)+27*gr(nb-1)+12.0*gr(nb-2)-
       >            8.0*gr(nb-3)+2.0*gr(nb-4))/35.0d0
         gr0(nb)=(69.0*gr(nb)+4.0*gr(nb-1)-6.0*gr(nb-2)+
       >          4.0*gr(nb-3)-gr(nb-4))/70.0d0
         end if
         gr = gr0
  
  
         dr = rmax/nb
         do k=1,nb
           write(fn_out,'(2F12.6)') 
  