下面以Si晶体为例，计算能带结构。

STEP 1

&control
    calculation = 'scf'
    restart_mode='from_scratch'
    prefix = 'si'
    outdir = './outdir'
    pseudo_dir = '/BIGDATA1/ac_iphy_jrsun_1/soft/QE/SSSP'
/
&system
    ibrav=2, celldm(1) =10.410909236, 
    nat=2, ntyp=1,
    ecutwfc=40
    ecutrho=320
    nbnd=8
    occupations='smearing', smearing='gaussian',degauss=0.005
/
&electrons
    conv_thr=1e-8
/
ATOMIC_SPECIES
 Si  28.0855  Si.pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS (alat)
 Si 0.00 0.00 0.00
 Si 0.25 0.25 0.25
K_POINTS (automatic)
  8 8 8 0 0 0

In si.0_scf.out, we can get the LUMO and HOMO:
highest occupied, lowest unoccupied level (ev): 5.7618 6.4467
(not very dense k-mesh)

We need to add the smearing as the $E_{f}$ can be everywhere in the gap. (However, in this way, we cannot get the HOMO and LUMO.)
the Fermi energy is 6.1499 ev

However, we do not use the smearing in STEP 1.

STEP 2

&control
    calculation = 'nscf'
    restart_mode='from_scratch'
    prefix = 'si'
    outdir = './outdir'
    pseudo_dir = '/BIGDATA1/ac_iphy_jrsun_1/soft/QE/SSSP'    
    ! pseudo_dir = '/home/anonymous/quantumEspresso_2019/SSSP_precision_pseudos'
/
&system
    ibrav=2, celldm(1) =10.410909236, 
    nat=2, ntyp=1,
    ecutwfc=40
    ecutrho=320
    occupations='tetrahedra'
    nbnd=8
/
&electrons
    conv_thr=1e-8
/
ATOMIC_SPECIES
 Si  28.0855  Si.pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS (alat)
 Si 0.00 0.00 0.00
 Si 0.25 0.25 0.25
K_POINTS (automatic)
  12 12 12 0 0 0

And we get the Fermi energy again.
the Fermi energy is 6.1330 ev

STEP 3

Cal the band structure with pw.x

&control
    calculation = 'bands'
    restart_mode='from_scratch'
    prefix = 'si'
    outdir = './outdir'
    pseudo_dir = '/BIGDATA1/ac_iphy_jrsun_1/soft/QE/SSSP'    
    ! pseudo_dir = '/home/anonymous/quantumEspresso_2019/SSSP_precision_pseudos'
/
&system
    ibrav=2, celldm(1) =10.410909236, 
    nat=2, ntyp=1,
    ecutwfc=40
    ecutrho=320
    nbnd=8
/
&electrons
    conv_thr=1e-8
/
ATOMIC_SPECIES
 Si  28.0855  Si.pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS (alat)
 Si 0.00 0.00 0.00
 Si 0.25 0.25 0.25
K_POINTS {crystal_b}
5
  0.0000 0.5000 0.0000 20 !L
  0.0000 0.0000 0.0000 30 !Gamma
  -0.500 0.0000 -0.500 10 !X
  -0.375 0.2500 -0.375 30 !U
  0.0000 0.0000 0.0000 20 !Gamma

Compared with calculations before, we change the type of calculation and the Kpoints with line-mode.

K_POINTS {crystal_b}
5
  0.0000 0.5000 0.0000 20 !L
  0.0000 0.0000 0.0000 30 !Gamma
  -0.500 0.0000 -0.500 10 !X
  -0.375 0.2500 -0.375 30 !U
  0.0000 0.0000 0.0000 20 !Gamma

The second line refers to the number of high-symmetry $k$ we used.The ‘20’ in third line means that there are 20 points from $L$ to $\Gamma$.

In this method, the band structure is calculated but not readable, so we need post-process.

STEP 4

Before three steps, we use the pw.x, now we use the bands.x

&bands
  outdir='./outdir/'
  prefix='si'
  filband='si.bands.dat'
/

Then we get the file si.bands.dat

STEP 5

Use the plotband.x

si.bands.dat
-7 16 !（范围）
si.bands.xmgr
si.bands.ps
6.1330 ! (Fermi E)
2 6.1330 ！ (刻度间隔，费米能)