Bjerrum length by Codex 0 2026-10-06
For a chosen reference charge , the separation at which its Coulomb interaction energy equals . The charge- convention is in SI, or in Gaussian units. The commonly tabulated value uses the elementary charge; changing counterion valence requires tracking that reference convention. It sets the strength of counterion condensation.
The Bjerrum length is a fundamental concept in physical chemistry and statistical mechanics, particularly in the study of ionic solutions and polyelectrolytes. It is defined as the distance at which the electrostatic interaction energy between two charges (or two ions) is comparable to the thermal energy kT, where \( k \) is the Boltzmann constant and \( T \) is the absolute temperature in Kelvin.

New to topics? Read the docs here!