srd fluid and lj fluid

Yes, I set two kind of ( polymer and wall) particles in the same group as follows:

atom_modify first big

group wall type 1
group polymer type 2
group fluid type 3
group big type 1 2

velocity wall set 0.0 0.0 0.0
velocity fluid create 1.0 87287 loop geom

bond_style fene
bond_coeff 1 60.0 1.5 1.2 1.0

pair_style lj/cut 2.5
pair_modify shift yes
pair_coeff 1 1 1.0 1.0 2.5
pair_coeff 1 2 1.0 1.0 1.12
pair_coeff 1 3 0.0 1.0 0.0
pair_coeff 2 2 1.0 1.0 1.12
pair_coeff 2 3 0.0 1.0 0.0
pair_coeff 3 3 0.0 1.0 0.0

fix 1 wall setforce 0.0 0.0 0.0
fix 2 polymer nve/sphere
fix 3 polymer langevin 1.0 1.0 10.0 904297
fix 4 fluid srd 50 big 1.0 0.25 34578 radius 0.85 sreach 0.2 collision slip inside ignore overlap yes

communicate multi group big vel yes
neigh_modify include big
Should not be both the wall and polymer particles in the same group?
If your answer is yes, what should i do?
Regards
Samira

yes, they should be in the same group. If you do
that and SRD particles pass thru the wall, then it means
you have "holes" in the wall. Overlap the wall particles
enough that there are no holes, but not so much that
you have 100s of big particles per SRD bin, and they
should be an effective wall.

Steve

How i can make a wall with enough overlap between its particles in order not to have holes in the wall?
What kind of style (sc,fcc,bcc,hcp,diamond) can i use to make that wall?

A 2d layer of an fcc of hcp lattice simply needs particles
big enough to overlap by 10 to 20% That's a math question, not a LAMMPS
question. Work out the math and dump the coordinates and
verify that you did it right.

Steve

I have made a wall with bcc or fcc style for my system before
But still srd particles can move thru the wall
I think this problem is for kind of interactions between srd/wall particles or maybe range of coefficients dont match correctly with diameters of wall particles?
Because i used a wall in lj fluid-wall-polymer system the same as i had used in srd fluid-wall-polymer system and lj fluid particles cannt move thru wall despite it has holes
samira

If the particles have big enough diameters relative
to the lattice constant, that should work. I.e. you
get a wall w/out holes. Whether you
chose correct parameters or not, I don't know.
Since you once chose parameters that gave you
far too many big particles per SRD bin, implying
huge overlaps, I'm guessing the problem is with
the parameters you are choosing.

Steve