Abstract: In density functional theory (DFT) quantum chemistry calculations, it is necessary to set parameters for the exchange-correlation functional. Consequently, electronic exchange interaction becomes an important physical quantity frequently mentioned in computational chemistry courses. To facilitate students’ better understanding of exchange interaction, this article uses helium and carbon atoms as examples to discuss the difference between exchange interaction and the common Coulomb interaction, explain why the exchange interaction originates from the Pauli exclusion principle, and illustrate how Hund’s rule can be understood through the exchange interaction.

Key words: Computational chemistry, Electronic exchange interaction, Pauli exclusion principle, Hund’s rule