Maxwell equilibrium velocity distribution
For a dilute classical ideal gas in its rest frame, the probability density of a particle velocity is (m/(2πk_BT))³ᐟ²exp[−m|v|²/(2k_BT)].
Key knowledge
For a dilute classical ideal gas in its rest frame, the probability density of a particle velocity is (m/(2πk_BT))³ᐟ²exp[−m|v|²/(2k_BT)]. The corresponding speed density includes 4πv², and mean translational kinetic energy is 3k_BT/2.
Values and equations
f(v⃗)=(m/(2πk_BT))³ᐟ²e^[−m|v⃗|²/(2k_BT)]; P(v)=4πv²f(v⃗)
- f
- Three-dimensional velocity probability density s³ m⁻³
- P
- Speed probability density s m⁻¹
- v,v⃗
- Speed and velocity m s⁻¹
- m
- Particle mass kg
- k_B
- Boltzmann constant J K⁻¹
- T
- Temperature K
Conditions and scope
- Nonrelativistic equilibrium particles of one mass m>0, T>0; ideal classical translational degrees of freedom.
- Drift adds a mean velocity; quantum degeneracy, strong interactions or nonequilibrium conditions require different models.
Sources · 1
References
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Evidence and review
Thermodynamics and Statistical Mechanics (2016): Maxwell velocity distribution: Equations 7.202–7.238: velocity-space distribution, speed distribution and moments; number density divided out to obtain a probability density.
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