Interface to the XTB program (github.com/grimme-lab/xtb, open source).

For now, the interface is ony very simple, implementing single-point and gradient calculations with GFN-xTB and GFN2-xTB methods, optionally with the GB solvent.

Warning

There had been various changes in the input and output over the history of xtb. The interface has been tested to be compatible with version 6.2.2.