Here is a vc-relax calculation example.
In this section, we are going to define the calculation type to 'vc-relax' instead of 'scf'.
'etot_conv_thr' is the convergence threshold on total energy (a.u) for ionic minimization. The default values for'etot_conv_thr' is 1.0D-4.
'forc_conv_thr' is the convergence threshold on forces (a.u) for ionic minimization. The default values for'forc_conv_thr' is 1.0D-3. To get better convergence, the example uses smaller values for 'etot_conv_thr' and 'forc_conv_thr'.
'nstep' is the number of molecular-dynamics or structural optimization steps performed in this run. The default value is 50.
'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.
The input difference between 'relax' and 've-relax' is 'relax' does not have ' &cell' section. In this section, the type of cell dynamics is deifned.
&control calculation='vc-relax', restart_mode='from_scratch', prefix='Bi', outdir='temp', pseudo_dir = '.', etot_conv_thr=1.0d-6, forc_conv_thr=1.0d-6, 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_beta =0.7, conv_thr =1.0d-8, / &ions ion_dynamics='bfgs' / &cell cell_dynamics='bfgs', press=0.0, press_conv_thr=0.5, / 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
- ↑ Quantum-espresso.org. (2019). pw.x: input description. [online] Available at: https://www.quantum-espresso.org/Doc/INPUT_PW.html [Accessed 19 Apr. 2019]