Hartree

The hartree (symbol: Eh or Ha), also known as the Hartree energy, is the atomic unit of energy, named after the British physicist Douglas Hartree. It is defined as 2R_∞hc, where R_∞ is the Rydberg constant, h is the Planck constant and c is the speed of light. The 2014 CODATA recommended value is E_h = 4.359 744 650(54)×10⁻¹⁸ J = 27.211 386 02(17) eV.^[1]

The hartree energy is approximately the electric potential energy of the 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 \epsilon _{0}\hbar }}\right)^{2}=m_{{\mathrm {e}}}c^{2}\alpha ^{2}={\hbar c\alpha \over {a_{0}}}

= 2 Ry

≜ 4.359 744 34(19)×10⁻¹⁸ J

≜ 27.211 385 05(60) eV

≜ 2625.499 62 kJ/mol

≜ 627.509 469 kcal/mol

≜ 219 474.631 3705(15) cm⁻¹

≜ 6 579.683 920 729(33) THz

≜ 3.157 746 46 x 10⁵ K

where:

a₀ is the Bohr radius,

c is the speed of light in vacuum, and

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