1.13 How do I calculate the equilibrium structure?

Use what='mur_lc'. See example05 for the cubic case and refer to the user's guide for anisotropic solids. The crystal parameters are written in the THERMO_PW output file. Note that the structure is searched interpolating with a polynomial or with the Murnaghan equation the energy calculated for several geometries close to the geometry given in the input of pw.x so the closer this structure to the actual equilibrium structure the better the fit and the closer the value found by THERMO_PW to the real minimum. You can check on the file output_mur.ps (when lmur=.true.) or output_energy.ps (when lmur=.false.) if the minimum is within the range of calculated structures. If it is not, the calculated minimum is probably inaccurate and it is better to repeat the calculation starting from it. Note also that almost all options can be specified using what='mur_lc_...' instead of what='scf_...'. In this case the calculations are carried out at the equilibrium geometry instead of the geometry given in the pw.x input. Setting a finite pressure in the THERMO_PW input, the equilibrium geometry is the one at the given pressure (see below) and the calculations are carried out at this geometry.