anchor.diff:       >               x,z,gamma,xr,zr,
        >               dxdn,dxdagr,dzdn,dzdtau,
        >               ec,fnc,fdnc,fdtauc)
  -
  -        ec     = 2.0d0*ec
  -        fnc    = 2.0d0*fnc
  -        fdnc   = 2.0d0*fdnc
  -        fdtauc = 2.0d0*fdtauc
   
   c      else
   c         ex = 0.0d0
  
positive.code:         call nwpw_GVT4(aa,bb,cc,dd,ee,ff,alpha,alpha,
       >              xr,zr,gamma,GG,dGdx,dGdz)
  
          ex     = 2.0d0*n_13*GG
          fnx    = 2.0d0*(frthrd*n_13*GG + n_43*(dGdx*dxdn + dGdz*dzdn))
          fdnx   = 2.0d0*n_43*(dGdx*dxdagr)
          fdtaux = 2.0d0*n_43*(dGdz*dzdtau) 
  
  ********* VS98 Correlation *********
  ********* Same-spin *********
  
negative.code:       call gen_PW92_BW_restricted(n2ft3d,rho_in,ec0,fnc0)
  
        do i=1,n2ft3d
          n       = rho_in(i) + ETA
          agr     = agr_in(i)
          tau     = tau_in(i)
          ec_LDA  = ec0(i)
          fnc_LDA = fnc0(i)
  
         !if (n .gt. tol)  then
  
  