Lower bound molecular orbitals for H, HeH⁺⁺, and H

Gaussian orbitals are used to calculate Temple lower bounds for H , HeH ++ , and H . Molecular orbitals are constructed from individual Gaussian‐type orbitals ( GTO ) and from GTO contractions adapted for either upper or lower bounds of the hydrogen atoms. The MOS are optimized by minimizing either the upper bound, 〈H〉, or the variance, 〈( H – E ) 2 〉. The best Temple lower bounds achieved by these methods are −0.60336 a.u. for , − 1.06224 a.u. for HeH ++ , and −0.13003 a.u. for H . Comparison is made with other types of molecular orbitals and with the exact wave functions for , HeH ++ . Analysis of the nuclear cusps is given. A prescription for constructing lower bound molecular orbitals is offered.