[gpaw-users] Funny electronic band structure

[Darío Fdez-Pello Lois]

Dear all,

Thanks for your replies, indeed it should be a colon after 'size', I
mistyped it somehow.

The requested figures are attached, please let me say that Mo_band.png
comes from the QE and ELK calculations while MoBandstructure.png comes from
GPAW.

In addition, here are the scripts:
-------SCF
import numpy as NP
from ase.lattice.cubic import BodyCenteredCubic
from gpaw import GPAW,PW,MethfesselPaxton,Mixer
from ase.io import read

k = 10
ecut = 600
N = 1
configs = read('MoStrain.traj@:')
aa = NP.array([config.cell[0, 0] for config in configs])
a = aa[-1]

mo = BodyCenteredCubic(size=(N,N,N),symbol='Mo',latticeconstant=a)
mo.calc = GPAW(mode=PW(ecut), xc='PBE', kpts={'size': (k,k,k),'gamma':
True}, setups={'Mo': '6'}, occupations=MethfesselPaxton(0.01),
mixer=Mixer(0.1, 1, 100), txt='bulk.txt')
mo.get_potential_energy()
mo.calc.write('bulk.gpw')

--------BAND
import numpy as NP
from ase.io import read, write
from ase.lattice.cubic import BodyCenteredCubic
from ase.dft.kpoints import ibz_points, get_bandpath
from gpaw import GPAW, PW, MethfesselPaxton
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

num_bands=12

calc = GPAW('bulk.gpw', fixdensity=True, usesymm=None,
convergence={'bands': num_bands}, maxiter=600, txt='band.txt')
points = ibz_points['bcc']
G = points['Gamma']
H = points['H']
N = points['N']
P = points['P']
kpts, x, X = get_bandpath([G, H, N, G, P], calc.atoms.cell, 200)
calc.set(kpts=kpts)
calc.get_potential_energy()
e_kn = NP.array([calc.get_eigenvalues(k) for k in range(len(kpts))])

# Plot the band structure

e_f = calc.get_fermi_level()
e_kn -= e_f
emin = -10 #e_kn.min() - 1.0
emax = 10 #e_kn[:, num_bands].max() + 1.0

plt.figure(figsize=(5, 6))
for n in range(num_bands):
    plt.plot(x, e_kn[:, n])
for p in X:
    plt.plot([p, p], [emin, emax], 'k-')
plt.plot([0, X[-1]], [0, 0], 'k-')
plt.xticks(X, ['$%s$' % n for n in ['\Gamma', 'H', 'N', '\Gamma', 'P']])
plt.axis(xmin=0, xmax=X[-1], ymin=emin, ymax=emax)
plt.xlabel('k-vector')
plt.ylabel('E - E$_F$ (eV)')
plt.title('Bandstructure of Mo')
plt.savefig('MoBandstructure.png')

--------------------
​END of scripts​


​Best regards,

   Darío​


2015-02-03 8:19 GMT+01:00 Jussi Enkovaara <jussi.enkovaara at csc.fi>:

> Hi Dario,
> could you be a bit more specific what's wrong with the band stucture
> (preferrably with a picture of correct / incorrect one), e.g are some bands
> fine but others not?
>
> In principle, your script below looks fine, but could you also provide the
> full scripts for SCF and band structure calculations?
>
> Best regards,
> Jussi Enkovaara
>
>
> On 2015-02-03 00:38, Darío Fdez-Pello Lois wrote:
>
>> Dear all,
>>
>> My question is related to the calculation of the electronic band structure
>> of molybdenum, which I was successfully able to reproduce both using a
>> full
>> potential code (ELK) and a plane wave one (Quantum Espesso).
>> Unfortunately,
>> the same doesn't happen when I use GPAW (with PW mode) resulting a quite
>> different structure.
>> Here are the relevant (I guess) lines, of course the obligatory
>> parameter's
>> convergence were peviouslly done:
>>
>> [ ... ]
>> mo=BodyCenteredCubic(size(N,N,N),symbol='Mo',latticeconstant=a)
>> mo.calc = GPAW(mode=PW(ecut),
>>        xc='PBE',
>>        kpts={'size'(k,k,k),'gamma': True},
>>        setups={'Mo': '6'},
>>        occupations=MethfesselPaxton(0.01),
>>        mixer=Mixer(0.1, 1, 100),
>>        txt='bulk.txt')
>> [ ... ]
>>
>> thereafter I run the band structure script similar to the one given in the
>> tutorial (with obvious changes: bcc instead of fcc, etc.)
>>
>> I am very confused at this point and I hope some of you would kindly give
>> me some insight.
>>
>> Best,
>>
>>    Darío.
>>
>>
>>
>>
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>> gpaw-users at listserv.fysik.dtu.dk
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>>
>>
>
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