Band structure of bulk graphene: Difference between revisions

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Line 8: Line 8:
from ase.io import read, write
from ase.io import read, write
from gpaw import GPAW, PoissonSolver, Mixer
from gpaw import GPAW, PoissonSolver, Mixer
from ase.lattice import bulk  
from ase.structure import bulk  




Line 18: Line 18:
gnr.positions=([[ 0. ,  0.,  0.], [ 1.23060,  0.7104873,  0. ]])
gnr.positions=([[ 0. ,  0.,  0.], [ 1.23060,  0.7104873,  0. ]])


write('gnr.traj', gnr)
write('gr.traj', gnr)


# Make self-consistent calculation and save results
# Make self-consistent calculation and save results
Line 24: Line 24:
             mode='fd', #finite difference(fd)
             mode='fd', #finite difference(fd)
             xc='PBE',
             xc='PBE',
            basis='szp(dzp)',
             kpts=(5,5,1),
             kpts=(5,5,1),
             occupations=FermiDirac(width=0.05, maxiter=2000),
             occupations=FermiDirac(width=0.05, maxiter=2000),
Line 87: Line 86:
from ase.io import read, write
from ase.io import read, write
from gpaw import GPAW, PoissonSolver, Mixer
from gpaw import GPAW, PoissonSolver, Mixer
from ase.lattice import bulk  
from ase.structure import bulk  


# -------------------------------------------------------------
# -------------------------------------------------------------
Line 97: Line 96:
gnr.positions=([[ 0. ,  0.,  0.], [ 1.23060,  0.7104873,  0. ]])
gnr.positions=([[ 0. ,  0.,  0.], [ 1.23060,  0.7104873,  0. ]])


#gnr.center()
write('gnr.traj', gnr)
write('gnr.traj', gnr)


Line 154: Line 152:
         print >>f, k, eps_skn[0, k, n]
         print >>f, k, eps_skn[0, k, n]
     print >>f
     print >>f
</pre>
</pre>

Latest revision as of 15:41, 17 November 2014

Graphene using grid

  • graphene_grid.py:
from gpaw import GPAW, FermiDirac
from ase import Atoms
from ase.io import read, write
from gpaw import GPAW, PoissonSolver, Mixer
from ase.structure import bulk 


# -------------------------------------------------------------
# Bulk configuration
# -------------------------------------------------------------

gnr = bulk('C', 'hcp', a=2.4612, c=6.709) # hexagonal close-packed (hpc)
gnr.positions=([[ 0. ,  0.,  0.], [ 1.23060,  0.7104873,  0. ]])

write('gr.traj', gnr)

# Make self-consistent calculation and save results
calc = GPAW(h=0.18,
            mode='fd', #finite difference(fd)
            xc='PBE',
            kpts=(5,5,1),
            occupations=FermiDirac(width=0.05, maxiter=2000),
            mixer=Mixer(beta=0.010, nmaxold=8, weight=100.0),
            poissonsolver=PoissonSolver(eps=1e-12),
            txt='band_sc.txt')

gnr.set_calculator(calc)
gnr.get_potential_energy()
calc.write('band_sc.gpw')



from ase.dft.kpoints import ibz_points, get_bandpath
points = ibz_points['hexagonal']
G = points['Gamma']
K = points['K']
M = points['M']
kpts, x, X = get_bandpath([K, G, M, K], gnr.cell, 60)

calc = GPAW('band_sc.gpw',
            mode='fd',
            kpts=kpts,
            txt='band_harris.txt',
            fixdensity=True,
            parallel={'domain': 1},
            eigensolver='cg', # 'cg' is allowed for grid method only
            usesymm=None,
            convergence={'bands': 'all'})

if calc.input_parameters['mode'] == 'lcao':
    calc.scf.reset()


calc.get_potential_energy()
ef = calc.get_fermi_level()
calc.write('band_harris.gpw')

# Extract eigenenergies into a file for plotting with some external package

import numpy as np

calc = GPAW('band_harris', txt=None)
eps_skn = np.array([[calc.get_eigenvalues(k,s)
                     for k in range(40)]
                    for s in range(1)]) - ef

f = open('bands.dat', 'w')
for n in range(8):
    for k in range(40):
        print >>f, k, eps_skn[0, k, n]
    print >>f

Graphene using LCAO

  • graphene_lcao.py:
from gpaw import GPAW, FermiDirac
from ase import Atoms
from ase.io import read, write
from gpaw import GPAW, PoissonSolver, Mixer
from ase.structure import bulk 

# -------------------------------------------------------------
# Bulk configuration
# -------------------------------------------------------------

gnr = bulk('C', 'hcp', a=2.4612, c=6.709)

gnr.positions=([[ 0. ,  0.,  0.], [ 1.23060,  0.7104873,  0. ]])

write('gnr.traj', gnr)

# Make self-consistent calculation and save results
calc = GPAW(h=0.18,
            mode='lcao',
            xc='PBE',
            basis='szp(dzp)',
            kpts=(5,5,1),
            occupations=FermiDirac(width=0.05, maxiter=2000),
            mixer=Mixer(beta=0.010, nmaxold=8, weight=100.0),
            poissonsolver=PoissonSolver(eps=1e-12),
            txt='band_sc.txt')

gnr.set_calculator(calc)
gnr.get_potential_energy()
calc.write('band_sc.gpw')

from ase.dft.kpoints import ibz_points, get_bandpath
points = ibz_points['hexagonal']
G = points['Gamma']
K = points['K']
M = points['M']
kpts, x, X = get_bandpath([K, G, M, K], gnr.cell, 40)

calc = GPAW('band_sc.gpw',
            mode='lcao',
            xc='PBE',
            basis='szp(dzp)',
            kpts=kpts,
            txt='band_harris.txt',
            fixdensity=True,
            parallel={'domain': 1},
            usesymm=None,
            convergence={'bands': 'all'})

if calc.input_parameters['mode'] == 'lcao':
    calc.scf.reset()

calc.get_potential_energy()
ef = calc.get_fermi_level()
calc.write('band_harris.gpw')

# Extract eigenenergies into a file for plotting with some external package

import numpy as np

calc = GPAW('band_harris', txt=None)
eps_skn = np.array([[calc.get_eigenvalues(k,s)
                     for k in range(40)]
                    for s in range(1)]) - ef

f = open('bands.dat', 'w')
for n in range(8):
    for k in range(40):
        print >>f, k, eps_skn[0, k, n]
    print >>f