  In this letter, using energy transfers, we demonstrate a route to
thermalization in an isolated ensemble of realistic gas particles. We performed
a grid-free classical molecular dynamics simulation of two-dimensional
Lenard-Jones gas. We start our simulation with a large-scale vortex akin to a
hydrodynamic flow and study its non-equilibrium behavior till it attains
thermal equilibrium. In the intermediate phases, small wavenumbers ($k$)
exhibit $E(k) \propto k^{-3}$ kinetic energy spectrum whereas large wavenumbers
exhibit $E(k) \propto k$ spectrum. Asymptotically, $E(k) \propto k$ for the
whole range of $k$, thus indicating thermalization. These results are akin to
those of Euler turbulence despite complex collisions and interactions among the
particles.
