anchor.diff:      integer :: m
       double precision :: x(3)
   
  +    call change_timer%tic()
       catalytic_change = 0
       !$omp parallel do private(x, dist_to_C_sq, dist_to_N_sq) reduction(+:catalytic_change)
       do m = 1, solvent% Nmax
  
positive.code:            ! this should be solved for a single passive colloid
             if ((.not. N_type) .or. (dimer)) then
                if (.not. on_track) then
                   call flag_timer%tic()
                   call flag_particles
                   call flag_timer%tac()
                   call change_timer%tic()
                   call change_species
                   call change_timer%tac()
                end if
             end if
          end if
  
negative.code:           end if
         end if
      end do
      call change_timer%tac()
  
    end subroutine change_species
  
  