Hi Martijn,

you are right, this email is not working any more, it was obviously deactivated recently. Sorry for the inconvenience! Please contact the support the 'usual' way. Or send it directly to me.

The $scftol keyword is mentioned as a way to solve SCF convergence problems in the FAQ, but this should be extended to general convergence problems - SCF, geometry optimizations (new to me but seems to be the case here), but also for e.g. vibrational frequencies, TDDFT or whenever one has to solve coupled perturbed HF/KS equations. It should be of importance only for cases with a very large amount of small contributions which sum up to something that contributes significantly.

If you have

- diffuse basis set

- complicated electronic structure

- higher derivatives of DFT functionals or a generally numerically challenging functional like SCAN

- a small lowest eigenvalue of the overlap matrix (too many basis functions at one place, e.g. using diffuse basis set for a fullerene which leads to a large number of basis sets inside)

- a lot of other things that do not come to my mind right now

convergence of whatever kind can be difficult. The most common ways to get around:

- tighter SCF and density convergence criteria,

- starting from a smaller basis set and then extending it to a large one while using the converged orbitals from the first job

- checking the input structure and running a pre-optimization with e.g. xtb (jobex -level xtb is very helpful in many cases)

- DFT: increased gridsize (m3 -> m4 or a non-m-grid size like 4), increased number of radial gridpoints (radsize 10 or 12 in $dft), more diffuse grid for diffuse basis set (diffuse 3 or diffuse 4 in the $dft section)

- tighter integral screening ($scftol 1d-15, $scftol 1d-16, ...)

- higher DIIS damping, but in a non-automated way, i.e. by checking that the damping is not too high such that one gets convergence just because the step size is too small

- increased orbital shift, but again, doing too much can give artificial convergence

- and probably a lot more technical tricks like fractional occupation numbers with $fermi (if you know some, please write them down in this topic)

Turbomole is a tool with pre-defined settings which do work quite well and quick in most cases, but there are a lot of adjustable screws.

Best Regards,

Uwe

PS: The fact that knocking down walls with your head is of no help should be noted in the FAQ, don't you think?