Q. How to check the convergence behavior in the SAC-CI optimization?

 

A. Please check the total energy and force at each iteration of the optimization. It is convenient to check the lines including the following expresstions.

   ECorr(SAC-CI-V)= …     Total energy= …

   Cartesian Forces:  Max …  RMS …

When the convergence of total energy is oscillating, please perform the single point calculation. Examine whether there are other excited states lying near the target state. It happens that the character of the target state exchanges due to such close lying excited states.