Hartree

The hartree (symbol: E_h), also known as the Hartree energy, is the unit of energy in the atomic units system, named after the British physicist Douglas Hartree. Its CODATA recommended value is E_h = 4.3597447222060(48)×10⁻¹⁸ J‍^[1] = 27.211386245981(30) eV.^[2]

The hartree is approximately the negative electric potential energy of the electron in a hydrogen atom in its ground state and, by the virial theorem, approximately twice its ionization energy; the relationships are not exact because of the finite mass of the nucleus of the hydrogen atom and relativistic corrections.

The hartree is usually used as a unit of energy in atomic physics and computational chemistry: for experimental measurements at the atomic scale, the electronvolt (eV) or the reciprocal centimetre (cm⁻¹) are much more widely used.

Other relationships

E_{\mathrm {h} }={\hbar ^{2} \over {m_{\mathrm {e} }a_{0}^{2}}}=m_{\mathrm {e} }\left({\frac {e^{2}}{4\pi \varepsilon _{0}\hbar }}\right)^{2}=m_{\mathrm {e} }c^{2}\alpha ^{2}={\hbar c\alpha  \over {a_{0}}}

= 2 Ry = 2 R_∞hc

= 27.211386245981(30) eV^[2]

= 4.3597447222060(48)×10⁻¹⁸ J^[1]

= 4.3597447222060(48)×10⁻¹¹ erg

≘ 2625.4996394799(50) kJ/mol

≘ 627.5094740631(12) kcal/mol

≘ 219474.63136320(43) cm⁻¹

≘ 6579.683920502(13) THz

where:

ħ is the reduced Planck constant,
m_e is the electron mass,
e is the elementary charge,
a₀ is the Bohr radius,
ε₀ is the electric constant,
c is the speed of light in vacuum, and
α is the fine-structure constant.

Effective hartree units are used in semiconductor physics where $e^{2}$ is replaced by $e^{2}/\varepsilon$ and $\varepsilon$ is the static dielectric constant. Also, the electron mass is replaced by the effective band mass $m^{*}$ . The effective hartree in semiconductors becomes small enough to be measured in millielectronvolts (meV).^[3]

References

^ ^a ^b "2022 CODATA Value: Hartree energy". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
^ ^a ^b "2022 CODATA Value: Hartree energy in eV". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
^ Tsuneya Ando, Alan B. Fowler, and Frank Stern Rev. Mod. Phys. 54, 437 (1982)

[physconst-Eh-1] "2022 CODATA Value: Hartree energy". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.

[physconst-EheV-2] "2022 CODATA Value: Hartree energy in eV". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.

[3] Tsuneya Ando, Alan B. Fowler, and Frank Stern Rev. Mod. Phys. 54, 437 (1982)

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