Abstract
The optical interband absorption of aluminium is calculated using a pseudopotential model with Ashcroft's empirical parameters. The calculation predicts an absorption peak at 1·55 eV in agreement with published experimental data. The predicted absorption is considerably sharper than that observed experimentally, but the areas under the absorption peaks agree within 10%. There is at present little experimental evidence for a second predicted absorption process centred at 0·55 eV.