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 Template:Physconst = Template:Physconst 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⁻¹) are much more widely used.

Other relationships

$E_{\mathrm{h}}=\frac{{\hslash }^2}{m_{\mathrm{e}}{a}_0^2}=m_{\mathrm{e}}{\left(\frac{e^2}{4\pi {\epsilon }_0\hslash }\right)}^2=m_{\mathrm{e}}{c}^2{\alpha }^2=\frac{\hslash c\alpha }{a_0}$

= 2 Ry = 2 R_∞hc

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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 $e^2/\epsilon$ and $\epsilon$ 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).