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# Hartree energy

The Hartree energy (symbol Eh) is a physical constant used as atomic unit of energy, named after physicist Douglas Hartree[?].

It has a value of twice the binding energy of the electron in the ground state of the hydrogen atom.

$E_h = {\hbar^2 \over {m_e a^2_0}}$
= 4.359 743 81(34) x 10-18J

where:

$\hbar$ is the Dirac's constant,
$m_e$ is the electron rest mass
$a_0$ is the Bohr radius

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