Band structure

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This example shows how to calculate the energy band structure. Similar to the DOS case, we first, do a ground-state energy calculation as in this example with one additional keyword in the INPUT file:

out_chg              1

this will produce the converged charge density, which is contained in the file SPIN1_CHG. Copy the file along with the STRU file, the pseudopotential file and the atomic orbital file (and the local density matrix file onsite.dm if DFT+U is used) to the new working directory where we will do a non-self-consistent calculation. In this example, the potential is constructed from the ground-state charge density from the proceeding calculation. Now the INPUT file is like:

INPUT_PARAMETERS
#Parameters (General)
ntype 1
nbands 8
calculation nscf
basis_type lcao
read_file_dir   ./

#Parameters (Accuracy)
ecutwfc 60
scf_nmax 50
scf_thr 1.0e-9
pw_diag_thr 1.0e-7

#Parameters (File)
init_chg file
out_band 1
out_proj_band 1

#Parameters (Smearing)
smearing_method gaussian
smearing_sigma 0.02

Here the the relevant k-point file KPT looks like,

K_POINTS # keyword for start
6 # number of high symmetry lines
Line # line-mode
0.5 0.0 0.5 20 # X
0.0 0.0 0.0 20 # G
0.5 0.5 0.5 20 # L
0.5 0.25 0.75 20 # W
0.375 0.375 0.75 20 # K
0.0 0.0 0.0 1 # G

This means we are using:

6 number of k points, here means 6 k points: (0.5, 0.0, 0.5) (0.0, 0.0, 0.0) (0.5, 0.5, 0.5) (0.5, 0.25, 0.75) (0.375, 0.375, 0.75) (0.0, 0.0, 0.0)
20/1 number of k points along the segment line, which is constructed by two adjacent k points.

Run the program, and you will see a file named BANDS_1.dat in the output directory. Plot it to get energy band structure.

If "outprojband" set 1, it will also produce the projected band structure in a file called PBAND_1 in xml format.

The PBAND1 file starts with number of atomic orbitals in the system, the text contents of element is the same as data in the BANDS1.dat file, such as:

<pband>
<nspin>1</nspin>
<norbitals>153</norbitals>
<band_structure nkpoints="96" nbands="50" units="eV">
...

The rest of the files arranged in sections, each section with a header such as below:

<orbital
index="                                       1"
atom_index="                                       1"
species="Si"
l="                                       0"
m="                                       0"
z="                                       1"
>
<data>
...
</data>

The shape of text contents of element is (Number of k-points, Number of bands)