The stationary determinant should be stable against orbital rotations: its orbital-energy Hessian must have no negative direction. A suitable local minimum, preferably the lowest accessible determinant of the appropriate symmetry and spin, can approximate the <ground state>; a stationary excited determinant or saddle generally cannot. Stability is still not a guarantee of small electron-correlation error.

Solution

Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2022 / Paper 4 / 60 / c / i / Solution

 Solution (source code)