Hartree

The hartree (symbol: Eh or Ha), also known as the Hartree energy, is the unit of energy in the Hartree atomic units system, named after the British physicist Douglas Hartree. Its CODATA recommended value is = 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. = 2 Ry = 2 R∞hc ≜ 27.211386245988eV ≜ 4.3597447222071e-18J ≜ 4.3597447222071e-11erg ≜ 2625.4996394799kJ/mol ≜ 627.5094740631kcal/mol ≜ 219474.63136320cm-1 ≜ 6579.683920502THz ≜ 315775.02480407K 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 and 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 millielectronvolts (meV).