Using g-xtb for geometry optimizations in Turbomole

[uwe]

Hello,

Turbomole, since a few releases, includes xtb (built from the sources from https://github.com/grimme-lab/xtb) as stand-alone tool, but also an earlier implementation which is included as a binary named tb.

Geometry optimizations with jobex at xtb level, running

jobex -level xtb

use the tb binary and not the xtb one. xtb itself includes a geometry optimizer, so it is often not necessary to combine jobex with xtb. Actually xtb is very Turbomole friendly as it directly works on Turbomole coord files.

The latest development of the Grimme group, g-xtb (https://github.com/grimme-lab/g-xtb) is currently available as binary version only. But since April 2026 it includes analytic gradients.

In order to run jobex with this new binary version, the attached jobex script does extend the official jobex by adding two new options:

jobex -level gxtb -gxtbopt "[xtb options]" ...

-gxtbopt is optional, but it allows to run xtb with additional settings (run xtb --help to get a list) like the charge (--chrg), unrestricted (--uhf), solvation (--cosmo water).

And, of course, most importantly, -gxtbopt is needed to tell xtb to use the new g-xtb method.

Example:

jobex -level gxtb -gxtbopt "--gxtb --cosmo water --chrg 1" -l /path/to/new-xtb/ -c 200

will run a geometry optimization:

• using g-xtb method
• with water as solvent
• total charge of +1
• using the xtb binary /path/to/new-xtb/xtb
• with a maximum number of geometry cycles of 200

Note: It is of course possible to run
    xtb coord --gxtb --opt
instead, this will be faster as no I/O is done during the optimization.
But there might be other reasons to use jobex. E.g. to open the result in TmoleX and visualize the complete geometry optimization as movie.

Enjoy and add a comment if something is not working as expected.

Regards, Uwe