secular equation

https://doi.org/10.1351/goldbook.ST07098
In molecular orbital theory, the determinant of matrix elements whose solution leads to the set of energy levels of molecular orbitals for a given system.
Source:
PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1962 (https://doi.org/10.1351/pac199971101919)