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 absolute value of binding energy of the electron in the ground state of the hydrogen atom |W1| or the ionization energy.
- = 4.359 743 81(34) × 10-18 J = 27.214 4 eV = 2 Ry
where:
is the Planck's constant,
- me is the electron rest mass
- a0 is the Bohr radius