"NAN Convergence criterion met"

Hello Q-Chem community,

I am performing SCF calculations with “BASIS2”, used to set the small basis set to use in basis projection (more information in Q-Chem 4.3 User’s Manual : Dual basis sets), as:

“JOBTYPE sp
EXCHANGE HF
BASIS def2-TZVP
BASIS2 STO-3G”

Although in the small basis set the convergence criterion is met, in the large basis set the SCF reaches a point where it says that the convergence criterion is met but the result is “Not a number”:

“177 -3492.4983546993 3.56E-08 Line search: overstep
178 -nan NAN Convergence criterion met”

Do you know what is going on in this situation? Thank you in advance for your time and help.

Regards,

Antonio

I you post the whole input, someone will take a look. Given the number of SCF cycles, something is clearly problematic about convergence in this case, and that’s usually the result of a poor guess (for whatever reason), so the solution is usually to try something different with the guess.