[gpaw-users] Phonon band structure

[Kristen Kaasbjerg]

I have now added a simple example to the ASE documentation illustrating
how to use the new phonon module:

https://wiki.fysik.dtu.dk/ase/ase/phonons.html#module-phonons

A few figures will be added soon.

Kristen


> Dear GPAW-users,
>
> I am a post-doc in Kyoto university in Japan. I work for phonopy.
> The Si band structure may be calculated as follows:
>
> from gpaw import GPAW
> from ase import *
> from ase.calculators import numeric_force
> from phonopy import Phonopy
> import numpy as np
>
> # GPAW setting
> a = 5.404
> bulk = Atoms(symbols='Si8',
>              positions=[(0, 0, 0),
>                         (0, 0.5, 0.5),
>                         (0.5, 0, 0.5),
>                         (0.5, 0.5, 0),
>                         (0.25, 0.25, 0.25),
>                         (0.25, 0.75, 0.75),
>                         (0.75, 0.25, 0.75),
>                         (0.75, 0.75, 0.25)],
>              pbc=True)
> bulk.set_cell((a, a, a), scale_atoms=True)
>
> n = 32
> calc = GPAW(gpts=(n, n, n),
>             nbands=8*3,
>             width=0.01,
>             kpts=(2, 2, 2),
>             convergence={'eigenstates': 1e-7}
>             )
>
> # Phonopy pre-process
> print "------"
> print "Phonon"
> print "------"
> # 1st arg. is the input unit cell.
> # 2nd arg. is the supercell lattice relative to the unit cell.
> # 'distance' is the distance of displacements.
> # Default symmetry tolerance is 1e-5 in fractional coordinates.
> phonon = Phonopy(bulk, [[1,0,0],[0,1,0],[0,0,1]], distance=0.01)
> symmetry = phonon.get_symmetry()
> print "Space group:", symmetry.get_international_table()
>
>
> phonon.print_displacements()
> supercells = phonon.get_supercells_with_displacements()
>
> # Force calculations
> set_of_forces = []
> for scell in supercells:
>     cell = Atoms( symbols=scell.get_chemical_symbols(),
>                   scaled_positions=scell.get_scaled_positions(),
>                   cell=scell.get_cell(),
>                   pbc=True )
>     cell.set_calculator(calc)
>     forces = cell.get_forces()
>     drift_force = forces.sum(axis=0)
>     print "        ---------------------------------"
>     print "     ", "%11.5f"*3 % tuple(drift_force)
>     # Simple translational invariance
>     for force in forces:
>         force -= drift_force / forces.shape[0]
>     set_of_forces.append(forces)
>
> # Phonopy post-process
> # 1st arg. is a relative lattice to the input unit cell.
> # 2nd arg. is bunch of the calculated forces.
> phonon.set_post_process([[0,0.5,0.5],[0.5,0,0.5],[0.5,0.5,0]], set_of_forces)
>
> # Phonon dispersion relation
> bands = []
>
> q_start  = np.array([0.5,0.5,0.0])
> q_end    = np.array([0.0,0.0,0.0])
> band = []
> for i in range(51):
>     band.append( q_start + ( q_end - q_start ) / 50 * i )
>
> bands.append(band)
>
> q_start  = np.array([0.0,0.0,0.0])
> q_end    = np.array([0.5,0.0,0.0])
> band = []
> for i in range(51):
>     band.append( q_start + ( q_end - q_start ) / 50 * i )
>
> bands.append(band)
>
> #*********************
> # Matplotlib required
> #*********************
> print "\nPhonon dispersion:"
> phonon.set_band_structure( bands )
> phonon.plot_band_structure().show()
>
>
>
>
>
> Togo
>
> On Fri, Dec 3, 2010 at 7:02 PM, Kristen Kaasbjerg <kkaa at fysik.dtu.dk> wrote:
>   
>> If someone finds it useful then why not ?
>> I should stress though, that the ASE implementation has features for
>> calculating phonon dispersion and mode visualization with ag.
>>
>> By the way, frophon code seem to have been replaced by the Phononpy code:
>> http://phonopy.sourceforge.net/
>>
>> Kristen
>>
>>     
>>> Hi,
>>>
>>> by looking at the latest abinit release one can see that they
>>> "Print out VASP-style POSCAR and FORCES files, for use with PHON or
>>> frophon codes for frozen phonon calculations."
>>> http://www.abinit.org/documentation/helpfiles/for-v6.4/release_notes/release_notes.html
>>>
>>> Could this way be also interesting for us?
>>> website of phon: http://www.homepages.ucl.ac.uk/~ucfbdxa/phon/
>>>
>>> Marcin
>>>
>>>       
>> _______________________________________________
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>>
>>     
>
>
>
>