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

[James Aston]

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 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.

Best wishes,
James


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