Influence of one region over other inspite of gap between atoms

Respected Lammps users, I am trying to melt a metal on the diamond contoured roughly textured surface. For this purpose I have developed simbox, region and then created atoms of both types. The y dimension of metal block is above the diamond but it is more distant than as defined by region command when visualized by ovito using measuring coordinates of iron. Moreover this also influences the melting procedure. The peaks coordinate measures of diamond substrate can be trimmed to 15 angstroms by shortening y dimension of diamond region. This whole interferes the melting process of iron on diamond substrate just 2 angstrom apart to be assumed as its melting above it.

set potential function and parameters

units metal
dimension 3
boundary p p p
atom_style atomic

neighbor 0.5 bin
neigh_modify delay 5

region simbox block -65 107 -1 299 -89 195 units box

variable x equal 21
variable y equal 35
lattice fcc 3.567
region substratediamond block -63 105 -85 103 -80 190 side in units box

variable xx internal 0.0
variable yy internal 0.0
variable v equal “(0.2v_yylat * cos(v_xx/xlat * 2.0PI4.0/v_x) + 0.5v_yylat - v_yy) > 0.0”

region ironball block -16 59 104 165 30 80 side in units box
#lattice bcc 2.856
lattice fcc 4.09

create_box 2 simbox

create_atoms 1 region substratediamond var v set x xx set y yy
create_atoms 2 region ironball

If the bolded numerals in region commands overlap each other even then the atoms don,t overlap but interferes simulation results.
Why and how regions are influencing each other?
Thanks for cooperation

This is not really a question about LAMMPS but about simulation methodology. That makes it off-topic for this forum and more a question to discuss with your adviser and collaborators. You may try the “Science Talk” category on MatSci in the future, but please refrain from posting similar questions in this category. Looking at multiple recent posts, this forum is running a very high risk of being abused as replacement for advisers or for doing science work on your own and that is not what should be.

There is not sufficient information here to make a proper analysis of the situation anyway, but the proverbial elephant in the room is the topic of interaction cutoffs.