  We have studied properties of a classical $N_S$-body double-well system
coupled to an $N_B$-body bath, performing simulations of $2(N_S+N_B)$
first-order differential equations with $N_S \simeq 1 - 10$ and $N_B \simeq 1 -
1000$. A motion of Brownian particles in the absence of external forces becomes
chaotic for appropriate model parameters such as $N_B$, $c_o$ (coupling
strength), and $\{\omega_n\}$ (oscillator frequency of bath): For example, it
is chaotic for a small $N_B$ ($\lesssim 100$) but regular for a large $N_B$
($\gtrsim 500$). Detailed calculations of the stationary energy distribution of
the system $f_S(u)$ ($u$: an energy per particle in the system) have shown that
its properties are mainly determined by $N_S$, $c_o$ and $T$ (temperature) but
weakly depend on $N_B$ and $\{\omega_n \}$. The calculated $f_S(u)$ is analyzed
with the use of the $\Gamma$ distribution. Difference and similarity between
properties of double-well and harmonic-oscillator systems coupled to finite
bath are discussed.
