The Einstein Relation  is an example of a fluctuation-dissipation relation.
The following formula is used: `D=muk_BT`, where:

• `mu` = mobility, or the ratio of the particle's terminal drift velocity to an applied force 
• `k_B` = Boltzmann's constant
• `T` = absolute temperature

References

Wikipedia (https://en.wikipedia.org/wiki/Einstein_relation_(kinetic_theory))