How to assign same pair-style/pair-coefficient/same mass to different group but same atom element type

Respected Lammps users, Hi, I am trying to simulate the melting of iron nanoparticles on the silicon substrate. Now I just only have two element types and hence two different atom types but one group of silicon substrate atoms and 12 spherical iron nanoparticle groups but just only one atom types.
My lammps version is 3 march, 2020.
Here is my script

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

lattice fcc 5.43
region substratesilicon block -63 105 -85 41 -80 190 side in units box

for iron

lattice fcc 2.9
region outer1 sphere -16 58 14 16 side in units box

region outer2 sphere 7.8 58 14 16 side in units box

region outer3 sphere 15.6 58 14 16 side in units box

region outer4 sphere -16 58 41 16 side in units box

region outer5 sphere -7.8 58 41 16 side in units box

region outer6 sphere -15.6 58 41 16 side in units box

region outer7 sphere -16 58 68 16 side in units box

region outer8 sphere -7.8 58 68 16 side in units box

region outer9 sphere -15.6 58 68 16 side in units box

region outer10 sphere -16 58 96 16 side in units box

region outer11 sphere -7.8 58 96 16 side in units box

region outer12 sphere -15.6 58 96 16 side in units box

create_box 13 simbox

mass 1 28.08
mass 2 55.84*

create_atoms 1 region substratesilicon
create_atoms 2 region outer1
create_atoms 3 region outer2
create_atoms 4 region outer3
create_atoms 5 region outer4
create_atoms 6 region outer5
create_atoms 7 region outer6
create_atoms 8 region outer7
create_atoms 9 region outer8
create_atoms 10 region outer9
create_atoms 11 region outer10
create_atoms 12 region outer11
create_atoms 13 region outer12

group silicon region substratesilicon
group iron region outer1
group iron region outer2
group iron region outer3
group iron region outer4
group iron region outer5
group iron region outer6
group iron region outer7
group iron region outer8
group iron region outer9
group iron region outer10
group iron region outer11
group iron region outer12

set group silicon type 1
set group iron type 2

pair_style hybrid eam lj/cut 17
**pair_coeff 1 1 none **
pair_coeff 22 22 eam Ag_u3.eam
pair_coeff 1 2 lj/cut 0.021 2.9

thermo 1
thermo_style custom step lx ly lz press pxx pyy pzz pe temp
thermo_modify norm yes
thermo_modify lost ignore flush yes

#minimize 1.0e-21 1.0e-21 10000 10000
timestep 0.001

velocity iron create 1500 12345 mom no rot no
run 0
velocity iron scale 1500

fix 1 iron nvt temp 1500 1500 0.1
fix 5 silicon setforce 0 0 0
#fix 3 silicon move linear 0 0 0

dump movie all atom 100 m.pase1
run 1100000

According to the above script I want to ask

1. May I assign the same group name iron to all the regions outer1 to outer12 because to avoid assigning the same fix 1 iron and velocity command many times to each different group for the same type of element iron atoms?
2. When I assign masses to two types of atoms iron and silicon I have in script. It shows all type masses are not set. May the asteric * symbol fix the problem to assign the same mass to type 2 iron atoms and hence the belongs to all 12 groups with region outer?
3. How can I assign the pair coefficients to just the two atoms types belonging to more than two groups as 13 groups in the script. As the mentioned type pair coefficient shows an error of all pair coefficients are not a set?

Thanks for cooperation

The number of elements and atom types are not necessarily coupled. You can have more atom types than elements (but not fewer) and those can carry different of the same settings.

Please wrap your input with triple backquotes (```) so it will be exempted from standard formatting which interprets certain special characters like * or # as formatting directives. That will make it correctly readable.

You say you are studying Iron, but use an EAM potential for gold.

You have created a system with 13 atom types (as is consistent with your intentions) and thus you need to provide pair coefficients for all 156 combinations of atom type pairs. See the documentation of the pair_coeff command.

The group command is incremental, so with each command (except for delete, of course) atoms are added to the group. Alternately you can create a union of multiple groups. See the group command documentation.

Please see the mass command documentation. The star in your input is placed wrong, anyway.

Respected Sir, You used “can have more atoms than elements and those can carry different” but is there any possibility to make them same because of no distinction present here with same setting to avoid cumbersome 156 combinations. If not then why these atoms types must be more than elements in the above case as I mentioned to apply same fix, same pair coefficient and same velocity command?

You are not paying attention.

There may be more atom types than elements, but there don’t need to be.
Besides, it is your create_box commands that defines that your system uses 13 atom types.
If you define so many atom types, you have to assign interactions to each of them.

When you have 13 atom types, you must provide interactions via pair_coeff for all of them, but the pair_coeff may use wildcards.

You have two alternatives to make atoms interact the same way:

  1. you assign them all the same atom type, oe
  2. you assign the same potential parameters and use the same pair style