给你随便找篇文献看吧。
http://www.iop.org/EJ/article/0295-5075/65/5/719/epl8055.html注意这里讲的:
The equilibrium colloid density $\rho (z)$ at height z follows, within a one-component picture, from the competition between minimal energy (all colloids at z=0, i.e. at the bottom) and maximum entropy (a homogeneous distribution in the available volume).
你能看明白吗?