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 Eh = 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
where:
- ħ is the reduced Planck constant,
- me is the electron rest 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.
Note that since the Bohr radius is defined as one may write the Hartree energy as in Gaussian Units where . Effective Hartree units are used in semiconductor physics where is replaced by where is the static dielectric constant. Also, the electron mass is replaced by the effective band mass . The effective Hartree in semiconductors becomes small enough to be measured in mili-electron volts (meV) [2]