would Coulombic cutoff length influence PPPM calculation while using water TIP4P/Ew model?


I am trying to simulate water molecules(TIP4P/Ew model) between two planar substrates. They will form a capillary bridge when the substrates are hydrophilic.

When I tried to change the cutoff length for Coulombic interaction(line 3), I get quite different shapes of capillary bridge
( e.g.,
I got contact angle around 70 degrees for Coulombic cutoff 9A

I got contact angle around 50 degrees for Coulombic cutoff 15A)

So my question is, how did the Coulombic cutoff influence the calculation of Coulombic interaction. Since I am using pppm, I shouldn’t get such big differences.

I might be doing it wrongly but I am not sure which part. Any advice would be appreciated.

The height between two planar substrates could be 20 Angstrom to 90 Angstrom.

Part of my input script is:
1 units real
2 atom_style full
3 pair_style lj/cut/tip4p/long 1 2 1 1 0.1250 9.0 12.0
4 pair_modify tail yes
5 boundary p p f
6 kspace_style pppm/tip4p 1.0e-5
7 kspace_modify slab 3.0
8 bond_style harmonic
9 angle_style harmonic
10 neighbor 2.0 bin
11 neigh_modify every 5 delay 0 check no
12 lattice fcc 3.5
13 region wallbottom block 0 75.0 0 75.0 0 1.7142
14 region walltop block 0 75.0 0 75.0 27.7142 29.7143