@ParmeetSinghEP066 I'm not too well versed in Quantum dots, but I would have thought the dot geometry would be very different than the bulk unit cell. I think if you can find a geometry specifically for a quantum dot, that would help things. It probably would be a little more spherical.

My experience is that the SCF not converging mid-way through a geometry optimization reflects that something is off with the starting geometry or possibly that the optimization took a bad step.

In the newer comments on your post, I believe Greg is assuming that the error you are printing, including the time, is for a single SCF cycle, which if it were taking 39 days would be exceedingly slow. But your calculation is completing a few opt steps before failing in the SCF.