[ase-users] GULP calculator in ASE with periodic boundary conditions

[Ask Hjorth Larsen]

Hi,

2018-01-16 18:05 GMT+01:00 James Aston via ase-users
<ase-users at listserv.fysik.dtu.dk>:
> Hello everyone,
>
> I am a PhD student at the University of Edinburgh and a new user of ASE. I
> am having trouble using the GULP calculator to determine the forces and
> phonon dispersion of a periodic crystal structure.
>
> I am currently trying to use the 8-Si example given here
> (https://github.com/atztogo/phonopy/blob/master/example/ase/8Si-phonon.py).
> I have set the calculator to calc = GULP(library='tersoff.lib',
> keywords="conp, gradient, fractional, nosymmetry").

(The examples in ASE use "conp gradient ...." without commas.  I infer
that probably it is supposed to work anyway though.)

>
> The code runs when periodic boundary conditions are set to false, albeit
> with negative phonon frequencies. When I set periodic boundary conditions to
> true I get an error from get_forces():
>
> 'ase.calculators.calculator.PropertyNotImplementedError: forces not present
> in this calculation'
>
> Does anyone know how to fix this? Thank you in advance.

Probably the forces are printed differently so the parser does not find them.

The parser looks only for "Final Cartesian derivatives".  Does your
output have that?

Best regards
Ask

>
> Best wishes,
> James
>
>
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