[Pw_forum] Input_keyword_Explanation[Basic]

[Abir Shadman]

Dear all,

I am a new user. I have gathered enough information from this forum to
write some codes. However i don't understand some keywords quite well.
Since i am from electrical background, i need to calculate band structure
properly because my goal is to find effective mass accurately which i will
use for transport calculation. Here is a bfgs relaxation code for bilayer
WS2 for my query purpose:

&CONTROL
      calculation = 'relax',
     restart_mode = 'from_scratch',
           outdir = 'G:\all_kk_QE\Quantum_Espresso\Quantum ESPRESSO 64-bit
5.1.2-mpich2\outdir',
           prefix = 'WS2Bilayer',
/
&SYSTEM

            ibrav = 0,

                a = 1.8,

              nat = 6,

             ntyp = 2,

      occupations = 'smearing',

         smearing = 'methfessel-paxton',

          degauss = 0.001,
          nspin=2,

          ecutwfc = 20,

          ecutrho = 160,

             nbnd = 30,
       starting_magnetization=0.6,


/

&ELECTRONS

         conv_thr = 1.0d-5,

      mixing_mode = 'plain',

      mixing_beta = 0.7,

  diagonalization = 'david',
  diago_full_acc = .true.

/

&IONS
ion_dynamics      = 'bfgs',
pot_extrapolation = 'second_order',
wfc_extrapolation = 'second_order',
upscale           = 100,
/

CELL_PARAMETERS
1.5 0.8660254038 0.00000
1.5 -0.8660254038 0.00000
0.0000 0.00000 15.0

ATOMIC_SPECIES
W 183.84 W.pbe-hgh.UPF
S 32.066 S.pbe-hgh.UPF

ATOMIC_POSITIONS (angstrom)
S       0.000000000  0.000000000   5.15
S       0.000000000  0.000000000   2
W       1.818653348  0.000000000   3.575
S       0.000000000  0.000000000   12.95
S       0.000000000  0.000000000   9.8
W       1.818653348  0.000000000   11.375

K_POINTS {automatic}
24 24 1   0 0 0

It's a well known system. It is put here because i want to know the meaning
of such inputs : occupations, smearing, degauss, mixing_mode,
mixing_beta, diagonalization
etc. in nutshell but yet comprehensive enough so that i can properly use
the values of these inputs for a unknown system.

​Best Regards​

Abir Shadman
Dept. of EEE,BUET.
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