anchor.diff:         solvent_pos(3,o) = solvent_pos(3,o)+colloids% pos(3,1)
          if (solvent% species(o)==2) then
             check = floor(solvent_pos(3,o)/dz)
  +          !$omp atomic
             conc_z(check) = conc_z(check) + 1
          end if 
       end do
  +
       colloid_pos(:,1) = 0
       colloid_pos(3,1) = colloids% pos(3,1)
       colloid_pos(:,2) = 0
  
positive.code:   double precision :: x(3)
    
    call random_number(rndnumbers)
    
    do  r = 1,solvent% Nmax
       if (solvent% species(r) == 1) then
         x = rel_pos(colloids% pos(:,1),solvent% pos(:,r),solvent_cells% edges) 
  
negative.code:        z_pos = dot_product(z, solvent_pos(:,o))
         solvent_pos(:,o) = (/x_pos,y_pos,z_pos/)
      end do
      !$omp parallel do private(r, theta, check)
      do o = 1, solvent% Nmax
         r = sqrt(solvent_pos(1,o)**2 + solvent_pos(2,o)**2)
         theta = atan(solvent_pos(2,o)/solvent_pos(1,o))
  