Dear researchers

I have a fundamental question about essence of NVE ensemble.

In that, we assume a constant number of particles are kept in fixed volume and their total energy is constant. This looks like having an isolated macroscopic system, like tea in an ideal flask, where no heat or work exchanges would occur.

However, unlike the macroscopic counterpart, one would expect temperature variation (drift) in the case of microscopic (atomic) system. In that case the total energy includes kinetic (KE) and potential (PE) components and temperature would continuously change as a result of KE exchange for PE.

So, I think that is a contradiction?

Why does atomic system under NVE not resemble the isolated, macroscopic system?

Could anybody please give me an illustrating explanation?

Many thanks in advance