Atom type-wise stress difference in multi element system

LAMMPS LAMMPS General Discussion
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Dear experts,

Greetings. I have a question related to the per atom stress calculation by lammps using snap potential (probably true for any form of IP) for multi element system. In relaxed unit cell I am getting different stress for each atype. For AB2 system stress/A and stress/B are equal but opposite (diagonal components). Each of them should be (near) Zero at equilibrium I guess. For a ternary system I am seeing that stress for A, B, and C are very different, however their sum is zero. That probably related to the lammps, how it calculate stress/atom.
I will be appreciated if someone kindly explain me more And if there any tips to visualize stress distribution in the deformed structure in multi element system.

Best regards,
Rana

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LAMMPS doesn’t pay much attention to the atom types when computing stress. The stress formalism that LAMMPS uses is “virial stress”. For that the contributions to the per-atom virial are taken from the distance vector \vec{r}_{ij} and the force vector \vec{F}_{ij} between pairs of atoms. Essentially the first sum in the definition of W_{ab} on the page compute stress/atom command — LAMMPS documentation

The other terms are for explicit bonded interactions, which are not present with SNAP.

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Why should this be the case? Even if the whole system is at an overall stress-free equilibrium, why should two different atom types with two different parameterizations have the same per-atom virial?