DCV-GCMD in lammps

Hi all,
I run some test about DCV-GCMD.
(1) fix gcmc to control the chemical potential or pressure of the two volume. And fix all nvt to induce the flow under the pressure difference. But I found the atom from region1 and region2 gather into some cluster in central region of system like. The input script is test1.in, and the snapshot is figure1.
(2) The same to (1), fix gcmc to control the chemical potential or pressure of the two volume. Three independent fix nvt in left, central and right region to induce the flow. But I found the atom from region1 seems not able to enter the region2 and the atom from region2 can not enter the region1. The input script is test2.in, and the snapshot is figure2.
I think the normal result of DCV-GCMD is that atoms from control volume can achieve anywhere in system. But, obviously, the two situation above are all incorrect. So, please, anyone could give me some suggestion to solve the problem.
Best wishes.
Dongbo Wang

figure1.png

figure2.png

test1.in (4.72 KB)

test2.in (4.84 KB)