Boltzmann's distribution

Statistical distribution of large numbers of small particles when subjected to thermal agitation and acted upon by electric, magnetic, or gravitational fields. In statistical equilibrium, the number of particles n per unit volume in any region is given by n=n ₀ exp(-E/kT), where k is Boltzmann's constant, T is absolute temperature, E is the potential energy of a particle in given region, and n ₀ is the number per unit volume when E=0. Also called Boltzmann principle