anchor.diff:   
   
   
  -       xce(i) 	= x_parameter*xe   + c_parameter*ce
  -       fn(i)	= x_parameter*fdnx  + c_parameter*fdnc
  -       fdn(i) 	= x_parameter*fdagrx + c_parameter*fdagrc
  +       xce(i) = x_parameter*xe   + c_parameter*ce
  +       fn(i)  = x_parameter*fdnx  + c_parameter*fdnc
  +       fdn(i) = x_parameter*fdagrx + c_parameter*fdagrc
   
         end do
   !$OMP END DO
  
positive.code:       real*8 DNS_CUT, ETA
        parameter (DNS_CUT        =      1.0d-18)
        parameter (ETA            =      1.0d-20)
  ****** Becke constants *****************************
        real*8 lda_c,beta
        parameter (beta = 0.0042d0)
  
negative.code: ******************************************************************
  *     *******calc. becke exchange energy density, fnx, fdnx*******
  *****************************************************************
            sd    = 1.0d0/(n_thrd*n) 
            chi   = two_thrd*agr*sd 
            if ((n.gt.tolrho)  .and.
       >        (agr.gt.minagr).and.
       >        (chi.lt.1.0d0)) then
               chi2  = chi*chi
               chiSQ = dsqrt(1.0d0+chi2)   
  
               K  = 6.0d0*beta*dlog(chi+chiSQ)
               F1 = chi2/(1.0d0+chi*K)
               xe = -n_thrd*(lda_c+beta*F1)/two_thrd
               F2 = (2.0d0 + chi*K-(chi2)*6.0d0*beta
       &             /chiSQ)
       &           /((1.0d0+chi*K)*(1.0d0+chi*K))
               fdnx = -(n_thrd/two_thrd)*dble(4.0d0/3.0d0)
       &               *(lda_c+beta*(F1-chi2*F2))
               fdagrx = -beta*chi*F2 
            else
               xe = -n_thrd*(lda_c)/two_thrd
               fdnx = -(n_thrd/two_thrd)*dble(4.0d0/3.0d0)*(lda_c)
               fdagrx = 0.0d0
            end if
         end if
  
  
  