Atómaeining

Atómaeining refers to a system of natural units used mainly in atomic physics and quantum chemistry to simplify the equations that describe atomic-scale phenomena. In this approach, several fundamental constants are set to unity, which makes the mathematical form of the Schrödinger equation and related expressions more compact and easier to manipulate.

The standard and most widely used variant is the Hartree atomic unit system. In these units, the electron mass m_e, the elementary charge e, the reduced Planck constant ħ, and the Coulomb’s constant 1/(4πε0) are all set to 1. As a result, derived units emerge naturally: the unit of length is the Bohr radius a0, the unit of energy is the Hartree Eh, and the unit of time is ħ/Eh. In practical terms, this means that numerical calculations for atoms and molecules can proceed without carrying many physical constants, until a final conversion back to SI units is required.

Values commonly cited in atomic units include a0 ≈ 0.5291772108 ångström, Eh ≈ 27.211386 eV, and a corresponding time unit t_H ≈ 2.4189×10^-17 s. Atomic units are widely used in computational chemistry and quantum physics because they streamline equations and reduce numerical error, but results must be translated back to SI units for reporting in most scientific contexts. The system is named after Douglas Hartree and represents one of several conventions for natural atomic units used in the field. See also: Hartree atomic units, Bohr radius, quantum chemistry.