Open GliderHX opened 3 years ago
Thanks for reporting. I'm currently working on a more stable and more complete PBC implementation at awvwgk/tblite, which is currently in the process of being interfaced with DFTB+. This implementation will at some point replace the current PBC implementation in xtb
which is not particular robust yet.
Regarding the halogen bonding term in GFN1-xTB. The term is particular difficult since it is a topological term which can be somewhat ill-defined under PBCs. I haven't come around to check how a periodic version of this contribution would look like yet.
There is now a periodic halogen bonding correction implemented in the tblite
library (https://github.com/awvwgk/tblite/commit/778f1c1623f52eca752f4fdeb1cbcb641e33ec76). I probably won't backport this to xtb
but just continue working on a full integration of the library into xtb
.
Describe the bug 1
xTB
6.3.0 version claims to support PBC calculation withGFN1
However, under version 6.4.0 (conda installation), I usedxtb --gfn 1 molcrystal.vasp
to calculate the periodic cell constructed with a molecule and reported the following errorTo Reproduce Steps to reproduce the behaviour:
xtb --gfn 1 molcrystal.vasp
Expected behaviour The unit cell containing
halogen atoms
can be calculated normally withxTB GFN 0
andCP2K GFN 1
Correction for halogen bonding is 0.0 a.u.
Describe the bug 2
When I use gfn 0 to calculate the same type of structure, it seems normal. But for one molecule, I constructed 634 different molecular crystals using force fields and recalculated their energies with
xtb gfn 0
.620/634 structures are in the range of -2.55 ~ - 2.65 eV/atom ( They are composed of the same molecule and should have a small energy difference). But there are 4 structures with energy less than -4 eV/atom, the most absurd one is - 331.39 eV/atom (the structure named POSCAR, which has been uploaded). So I doubt the accuracy of
xtb gfn 0
to calculate PBC structures.To Reproduce Steps to reproduce the behaviour:
xtb --gfn 0 POSCAR
Expected behaviour This problem structure is calculated normally using
CP2K GFN 1
andVASP
Additional context molcrystal.vasp POSCAR