&control

In this section, we are going to define the calculation type to 'relax' instead of 'scf'. 'nstep' is the number of molecular-dynamics or structural optimization steps performed in this run. The default value is 50.[1]


&system

'ecutrho' is kinetic energy cutoff (Ry) for charge density and potential. The default value is 4*'ecutwfc'. However, a larger value (8 to 12 times 'ecutwfc') is typically used.


&electrons

The default mode for'mixing_mode' is 'plain'and the default number for 'mixing_beta' which is mixing factor for self-consistency is 0.7. 'conv_thr' is the convergence threshold for selfconsistency: estimated energy error < conv_thr. The default value is 1.D-6.


&ions

The section is to define the type of ionic dynamics. The default for 'ion_dynamics' is 'bfgs'.

 &control
    calculation='relax',
    restart_mode='from_scratch',
    prefix='Bi',
    outdir='temp',
    pseudo_dir = '.',
    nstep=100
/
 &system    
    ibrav= 5, celldm(1) =8.979, celldm(4) =0.538, nat= 2, ntyp= 1,
    ecutwfc =60.0, ecutrho =720.0,
    occupations='smearing', smearing='mp', degauss=0.06
/
 &electrons
    mixing_mode='plain'
    conv_thr  =1.0d-8,
    mixing_beta  =0.7,
/
 &ions
    ion_dynamics='bfgs'
/
ATOMIC_SPECIES
 Bi  208.9804 Bi.pbe-dn-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS (crystal)
 Bi 0.2673 0.2673 0.2673 
 Bi 0.7327 0.7327 0.7327
K_POINTS automatic
 19 19 19 0 0 0   

Reference

1. Quantum-espresso.org. (2019). pw.x: input description. [online] Available at: https://www.quantum-espresso.org/Doc/INPUT_PW.html [Accessed 19 Apr. 2019]