freeelectronlike
Freeelectronlike describes electronic states in a solid that behave similarly to free electrons. In practice, it refers to bands whose energy-versus-momentum dispersion is close to parabolic and whose effective mass is near the bare electron mass. This behavior emerges when the lattice potential is weak or when electrons are highly delocalized, so Bloch states resemble plane waves.
In the nearly free-electron model, conduction electrons move in a uniform positive background. The energy as
Where observed: Alkali metals such as sodium and potassium are classic examples of free-electronlike conduction bands.
Limitations and deviations: Real materials have a periodic lattice potential that produces band structure and gaps,
See also: nearly free electron model, free-electron model, effective mass, jellium, band structure.