[lammps-users] Fluctuated stress during relax

Hi everyone,

I met a strange problem when I simulate two bulks material system, like NiAl. The interface will be formed during energy minization, however, when I increase the temperature to 300K, and keep it as constant, and relax the whole system under NVE, I input the average stresses of interface atoms and find out that there is fluctuation during relax. The magnitude of the stress fluctuation is comparable with the stress wave I want to apply later. So I want to know why this phenomenon exists and is it normal in two materials case, since there is no such phenomenon when I simulat one single materal.