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Chemistry · Glossary

What is Density of states and Fermi level?

Also known as: density of states · Fermi level

Definition 22.3 University Chemistry — Year 3 · Chapter 22 — Solid-State Chemistry: Bands, Defects and Semiconductors

The density of states g(E)g(E) is the number of levels per unit energy (and per atom or per unit volume) near the energy EE. The Fermi level EFE_F is the energy at which a level has probability 1/21/2 of being occupied; at zero temperature all levels below it are filled and all above it empty.

Hückel levels of chains of 2 to 64 atoms (one short line per level; with < 0 the bonding levels are at the bottom). The levels crowd into a band between + 2 and - 2; on the right, the density of states of the infinite chain, largest at the band edges.
Hückel levels of chains of 2 to 64 atoms (one short line per level; with β<0\beta < 0 the bonding levels are at the bottom). The levels crowd into a band between α+2β\alpha + 2\beta and α−2β\alpha - 2\beta; on the right, the density of states of the infinite chain, largest at the band edges.
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