Slater-type orbital

https://doi.org/10.1351/goldbook.S05710
An approximate @A00500@ attempts to allow for electron-electron repulsion by scaling the nuclear charge for each orbital.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1164 [Terms] [Paper]