Transport coefficient

A transport coefficient measures how rapidly a perturbed system returns to equilibrium.

The transport coefficients occur in transport laws where:

is a flux of the property
the transport coefficient of this property
, the gradient force which acts on the property .

Transport coefficients can be expressed via a Green–Kubo relation:

where is an observable occurring in a perturbed Hamiltonian, is an ensemble average and the dot above the A denotes the time derivative.[1] For times that are greater than the correlation time of the fluctuations of the observable the transport coefficient obeys a generalized Einstein relation:

In general a transport coefficient is a tensor.


See alsoEdit


  1. ^ Water in Biology, Chemistry, and Physics: Experimental Overviews and Computational Methodologies, G. Wilse Robinson, ISBN 9789810224516, p. 80, Google Books