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• QE_tutorial/Al へ行く。
  • 1 (2019-02-03 (日) 15:12:54)
  • 2 (2019-02-03 (日) 15:27:12)
  • 3 (2023-01-23 (月) 11:56:56)

* Aluminum in the fcc structure [#m3bcb1c5]
In this tutorial how to perform the total energy calculation of a metallic system is described by taking Al as an example. We use von Barth-Car normconserving pseudopotential as distributed in the Quantum-ESPRESSO web page.

** Optimizing the cell parameter [#i5a39f25]
In this example, the cell is optimized by using 'vc-relax.' Cutoff energy of 30 Ry and nonshifted 12 x 12 x 12 are used. In the metallic systems, the smearing technique is used with the keywords "occupation='smearing'", "smearing", and "degauss" with the number of bands ("nbnd") slightly larger than the half of the number of bands to accomodate partially unoccupied bands. How to determine the parameters for the smearing technique is discussed below.
 &control
  calculation  = 'vc-relax'
  restart_mode = 'from_scratch',
  pseudo_dir   =  '/home/ikutaro/QE/pseudo/'
  outdir       = './tmp'
  prefix       = 'al'
  tprnfor      = .true.
  tstress      = .true.
 /
 &system
  ibrav       = 2
  A           = 4.020
  nat         = 1
  ntyp        = 1
  ecutwfc     = 30.0
  ecutrho     = 120.0
  occupations = 'smearing'
  smearing    = 'mp'
  degauss     = 0.01
  nbnd        = 12
 /
 &electrons
  diagonalization = 'cg'
  conv_thr        = 1.0e-12
  mixing_beta     = 0.5
 /
 &ions
  ion_dynamics='bfgs'
 /
 &cell
  cell_dynamics='bfgs'
 /
ATOMIC_SPECIES
 Al 0.0000 Al.pz-vbc.UPF
ATOMIC_POSITIONS (crystal)
Al      0.000000000000      0.000000000000      0.00000000000
K_POINTS (automatic)
16 16 16 0 0 0
~

** Determining the smearing width [#i5b1b12c]

*** Exercise [#j649ff6a]