Enter the value in atomic units and select the energy unit type to determine the equivalent value in electronvolts (eV).
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Atomic Units to eV Formula
The following formulas are used to convert atomic units of energy into electronvolts (eV).
E(eV) = E(a.u.) × 27.2114
E(eV) = E(Ry) × 13.6057
Variables:
- E(eV) is the energy in electronvolts
- E(a.u.) is the energy in atomic units, typically Hartree
- E(Ry) is the energy in Rydberg units
- 27.2114 is the conversion factor from Hartree to eV
- 13.6057 is the conversion factor from Rydberg to eV
To calculate the energy in eV, multiply the energy value in atomic units by the appropriate conversion factor.
What are Atomic Units and eV?
Atomic units are a natural unit system used in quantum chemistry and atomic physics. In this system, several fundamental constants are normalized to 1, making equations easier to work with. The Hartree is the standard atomic unit of energy, while the Rydberg is another commonly used energy unit closely related to the Hartree. Electronvolts (eV) are more widely used in chemistry, spectroscopy, and solid-state physics because they provide a convenient scale for describing atomic and molecular energies.
How to Convert Atomic Units to eV?
The following steps outline how to convert atomic units of energy to electronvolts.
- First, determine the numerical energy value in atomic units.
- Next, identify whether the value is given in Hartree or Rydberg.
- Use the correct formula: multiply Hartree values by 27.2114 or Rydberg values by 13.6057.
- After calculating the result, compare your answer with the converter above.
Atomic Units to eV Conversion Table
The table below lists several example conversions using Hartree and Rydberg values.
| Energy in Atomic Units | Conversion Factor | Value in eV |
|---|---|---|
| 0.1 Eₕ | 27.2114 eV per Eₕ | 2.7211 eV |
| 0.5 Eₕ | 27.2114 eV per Eₕ | 13.6057 eV |
| 1 Eₕ | 27.2114 eV per Eₕ | 27.2114 eV |
| 2 Eₕ | 27.2114 eV per Eₕ | 54.4228 eV |
| 5 Eₕ | 27.2114 eV per Eₕ | 136.0570 eV |
| 10 Eₕ | 27.2114 eV per Eₕ | 272.1140 eV |
| 1 Ry | 13.6057 eV per Ry | 13.6057 eV |
Many quantum chemistry programs report total electronic energies in Hartree, while many reference values in experimental chemistry and physics are listed in eV. Because the conversion factors are fixed constants, it is straightforward to move between these unit systems for comparison and analysis.
Example Problem:
Use the following values as an example problem to test your knowledge.
Energy = 2 Hartree
Conversion Factor = 27.2114 eV per Hartree
Result = 54.4228 eV