xtb is supposed to throw a lot of feature-not-implemented errors at
you as you try out the very recently added periodic boundary conditions.
You can make use of the C-API and the ASE calculator class to get around this
errors for now, but we promise to add more features and runtypes in the future.
We support Turbomole’s coordinate files in a
riper compatible format.
It requires to have the
$periodic information, one of
and, of course, a
$coord data group present.
In contrast to Turbomole we want them all in one file,
file=<elsewhere> does not work with
A valid input for diamond is
$periodic 3 $cell angs 3.570 3.570 3.570 90 90 90 $coord angs 0.00000 0.00000 0.00000 C 0.89250 0.89250 0.89250 C 1.78500 1.78500 0.00000 C 2.67750 2.67750 0.89250 C 1.78500 0.00000 1.78500 C 2.67750 0.89250 2.67750 C 0.00000 1.78500 1.78500 C 0.89250 2.67750 2.67750 C $end
or using different keywords and order like for calciumfluoride here
$coord frac 0.250000000 0.250000000 0.250000000 f 0.750000000 0.750000000 0.750000000 f 0.000000000 0.000000000 0.000000000 ca $lattice angs 3.153833580 1.115048556 1.931320751 0.000000000 3.345145667 1.931320751 0.000000000 0.000000000 3.862641503 $periodic 3 $end
we do not care if you
$end your file or maybe even all your
data groups, since the parser politely ignores its presence.
While this format in principle is able to specify also 1D and 2D periodic
xtb does not support them right now.
Both Vasp 4 and Vasp 5 POSCAR and CONTCAR files are supported, but we require to have the information on the atomtypes present in the file. For details on the format refer to the documentation of Vasp.
You can use
ase convert to bring your
into Vasp format, as
xtb currently cannot read them.
feature implemented in version 6.2
To perform geometry optimizations with
xtb on periodic systems we
recommend to use an input file like
$opt engine=inertial $end
Since the ANC optimizers do not support periodic boundary conditions right now, use the inertial relaxation procedure instead.
The optimization log is written in Vasp 5 POSCAR format and contains the current energy and gradient norm in the first (comment) line.