Free-electron Fermi scale and low-temperature heat capacity
For noninteracting spin-½ electrons in a three-dimensional volume, k_F=(3π²n)¹ᐟ³ and E_F=ħ²k_F²/(2m).
Key knowledge
For noninteracting spin-½ electrons in a three-dimensional volume, k_F=(3π²n)¹ᐟ³ and E_F=ħ²k_F²/(2m). At T≪E_F/k_B, the electronic heat capacity at fixed N,V is C_V≈(π²/2)Nk_B(k_BT/E_F), reflecting excitations near the Fermi surface.
Values and equations
k_F=(3π²n)¹ᐟ³; E_F=ħ²k_F²/(2m); C_V≈π²Nk_B²T/(2E_F)
- k_F
- Fermi wavenumber m⁻¹
- n
- Electron number density m⁻³
- E_F
- Fermi energy J
- m
- Particle mass kg
- ħ
- Reduced Planck constant J s
- N
- Electron count
- k_B
- Boltzmann constant J K⁻¹
- T
- Temperature K
- C_V
- Electronic heat capacity J K⁻¹
Conditions and scope
- Twofold spin degeneracy, parabolic free-particle dispersion, large uniform volume and no applied splitting.
- This is a simple metal model; band geometry, interactions and magnetic order alter the density of states, effective masses and heat capacity.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Richard Fitzpatrick / University of Texas at Austin2 sources
Evidence and review
Thermodynamics and Statistical Mechanics (2016): Conduction electrons in metal: Equations 8.135–8.144: dispersion and Fermi-state counting; excludes its order-of-magnitude 3/2 heat-capacity estimate and universal valence-density inference. Thermodynamics and Statistical Mechanics (2016): Sommerfeld expansion: Equations 8.183–8.191: fixed-N low-temperature chemical potential, mean energy and π²/2 heat-capacity coefficient; not the source's extrapolation of low-T accuracy to T≈T_F.
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Entry details
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- physics-free-fermi-gas
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