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16.9.1 Level shifts


A level shift of shifta and shiftb hartree for $\alpha$- and $\beta$-spin orbitals, respectively, is applied. This can improve convergence, but has no effect on the solution. shifta$=-0.2$ to $-0.3$ are typical values. The defaults are shifta$=0$ and shifta$=-0.3$ in closed and open-shell calculations, respectively, and shiftb$=0$.

Applying large negative level shifts like {rhf; shift,-1.0,-0.5} will often stabilize convergence at the expense of making it somewhat slower. See section 16.10. 2018-06-18