Boltzmann constant

The Boltzmann constant ($k$ or $k_{B}$) is the physical constant relating temperature to energy. It is named after the Austrian physicist Ludwig Eduard Boltzmann. Its experimentally determined value (in SI units, 2002 CODATA value) is:

$k_{B}=1.3806505(24)\times 10^{-23}$ $\left.JK^{-1}\right.$

$=8.617343(15)\times 10^{-5}$ $\left.eV\right.$ $\left.K^{-1}\right.$

In units with molecular significance it is close to 1, for example see: DL_POLY units.

History of Boltzmann's constant

"This constant is often referred to as Boltzmann's constant, although, to my knowledge, Boltzmann himself never introduced it - a peculiar state of affairs, which can be explained by the fact that Boltzmann, as appears from his occasional utterances, never gave thought to the possibility of carrying out an exact measurement of the constant."

Max Planck, Nobel Lecture, June 2, 1920

See also

• C. Daussy, M. Guinet, A. Amy-Klein, K. Djerroud, Y. Hermier, S. Briaudeau, Ch. J. Bordé, and C. Chardonnet "Direct Determination of the Boltzmann Constant by an Optical Method", Physical Review Letters 98 250801 (2007)