[ase-users] Question about error in VASP calculator

[Tristan Maxson]

I think the problem arises from doing something like fcc111("Pt") and
getting a surface with the z-direction being non-periodic.  VASP users
don't have the option to set which directions are periodic so I also agree
personally that this property should more or less be ignored.  This is the
sort of thing that tends to cause weird problems for new users who aren't
even aware that the PBC property is there (because they don't need it since
they only work in VASP for example).  It makes sense in codes which do
something different with PBC set, but in codes that don't support PBC it
should throw a warning rather than throwing an exception.

As a middle ground, we could make a tag on the VASP calculator of
"ignore_pbc" to make it easy to write into the calculator definition that
we are ignoring pbc.

Thank you,
Tristan Maxson


On Fri, Jun 3, 2022 at 11:56 AM Gaël Donval via ase-users <
ase-users at listserv.fysik.dtu.dk> wrote:

> Hi both,
>
> The reason it's like this is Vasp is using planewaves and is intrinsically
> 3D periodic.
>
> There should be no reason ever to use a less-than-3D input file for use
> with Vasp or if that's the case, you have to specify how your less-than-3D
> structure must be converted to an approximately equivalent 3D one. There is
> *always* some amount of manual intervention involved. If that transform was
> unambiguous and unique, a warning might have been enough.
>
> What I suggest instead is defining a function to explicitly transform
> non-pbc structures into 3D-periofic-with-vacuum ones, setting all pbcs to
> true. If it's not already in ASE, I would definitely be for adding
> something like that somewhere like in ase.geometry. It's clean, it does
> what you want and it does not have to break any assumption anywhere.
>
> I also want to stress that
>
> struct.pbc = True
>
> is literally all you have to write if you don't care. ase.io.read might
> even have a pbc argument (don't quote me on this, I'm unsure).
>
> Again, pbc is an important property and lying about them to everyone
> depending on the calculator is not a good idea.
>
> Best,
> Gaël
>
>
>
>
>
>
> -------- Original Message --------
> On 3 Jun 2022, 10:55, Petr Grigorev via ase-users <
> ase-users at listserv.fysik.dtu.dk> wrote:
>
>
> Hello everyone,
>
> I oftenly use VASP in the scenario described by Jonas and would agree with
> him that warning would be more suitable.
>
> Best regards,
> Petr
>
> Le ven. 3 juin 2022 à 10:02, Jonas Björk via ase-users <
> ase-users at listserv.fysik.dtu.dk> a écrit :
>
>> Hi!
>>
>> “Recent” versions of the VASP calculators give the following error when
>> the Atoms object does not have periodic boundary conditions in all three
>> directions:
>>
>> ase.calculators.calculator.CalculatorSetupError: Vasp cannot handle
>> non-periodic boundaries. Please enable all PBC, e.g. atoms.pbc=True
>>
>> It seems a bit unnecessary. In some cases it is convenient to have the
>> PBC of the Atoms object set in 1D or 2D even when performing calculations
>> with VASP using vacuum in directions of non-periodicity, just to store
>> information about the material’s periodicity.
>>
>> To me, it seems appropriate to replace this error message with a warning.
>>
>> Best wishes,
>> Jonas
>>
>>
>> ---------------------------------------------------------------------
>> Jonas Björk, PhD
>> Senior Lecturer of Theoretical Chemistry
>>
>> Materials Design Division
>> Department of Physics Chemistry and Biology, IFM
>> Linköping University
>> Sweden
>>
>> Phone: +46 13 28 25 61
>> Google scholar: https://bit.ly/3GvptJQ
>> ---------------------------------------------------------------------
>>
>>
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