HOMO-LUMO Gap Calculator
Calculate the HOMO-LUMO gap, chemical reactivity descriptors, and optical properties from frontier orbital energies.
Orbital Energies
Highest Occupied Molecular Orbital
Lowest Unoccupied Molecular Orbital
Typical Values (eV)
Benzene: Gap ≈ 5.4 eV
Fullerene C60: Gap ≈ 1.9 eV
Polyacetylene: Gap ≈ 1.4 eV
HOMO-LUMO Gap
5.3000 eV
Insulator
Gap (kJ/mol)
511.37
Gap (Hartree)
0.1948
Wavelength (λ)
233.9 nm
Optical Property
UV absorber (<400 nm)
Reactivity Descriptors
Chemical Hardness (η)
2.6500 eV
Softness (S)
0.1887 eV⁻¹
Chemical Potential (μ)
-3.8500 eV
Electrophilicity (ω)
2.7967 eV
Formulas
Gap = E_LUMO - E_HOMO
η = (E_LUMO - E_HOMO) / 2
μ = (E_HOMO + E_LUMO) / 2
ω = μ² / (2η)
About HOMO-LUMO Gap
The HOMO-LUMO gap is the energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). This gap is crucial for understanding chemical reactivity, optical properties, and electronic conductivity. A larger gap indicates greater kinetic stability and lower chemical reactivity. The gap also determines the wavelength of light a molecule can absorb, making it important for photochemistry and materials science.