Editing Electronic band structure (section)

=== Density of states ===

{{Main|Density of states}}

The density of states function {{math|''g''(''E'')}} is defined as the number of electronic states per unit volume, per unit energy, for electron energies near {{math|''E''}}.

The density of states function is important for calculations of effects based on band theory.
In [[Fermi's golden rule|Fermi's Golden Rule]], a calculation for the rate of [[optical absorption]], it provides both the number of excitable electrons and the number of final states for an electron. It appears in calculations of [[electrical conductivity]] where it provides the number of mobile states, and in computing electron scattering rates where it provides the number of final states after scattering.{{Citation needed|date=October 2015}}

For energies inside a band gap, {{math|1=''g''(''E'') = 0}}.