The hartree (symbol: E<sub>h</sub>), 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 = The name "hartree" was suggested for this unit of energy.
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<sup>−1</sup>) are much more widely used.
Other relationships
: <math>E_\mathrm{h} = {\hbar^2 \over {m_\mathrm{e} a^2_0 = 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 </math>
:: = 2 Ry = 2 R<sub>∞</sub>hc
:: =
:: =
:: =
:: ≘ <!-- to be recalculated or used -->
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where:
- ħ is the reduced Planck constant,
- m<sub>e</sub> is the electron mass,
- e is the elementary charge,
- a<sub>0</sub> is the Bohr radius,
- ε<sub>0</sub> 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 <math>e^2</math> is replaced by <math>e^2/\varepsilon</math> and <math>\varepsilon </math> is the static dielectric constant. Also, the electron mass is replaced by the effective band mass <math>m^*</math>. The effective hartree in semiconductors becomes small enough to be measured in millielectronvolts (meV).
See also
- Rydberg constant