This option can be controlled by the following variables:

ngeo(1),...,ngeo(6) : the number of geometries to use for each celldm parameter. The lattice constant of these geometries is calculated from the input of pw.x. celldm(1),...,celldm(6) of this input is used for the central geometry. For the others celldm(1), ...,celldm(6), are changed in steps of step_ngeo(1), ...,step_ngeo(6). ngeo(1) must be odd. Only the values of celldm relevant for each Bravais lattice are actually changed. Default: integer 1,1,1,1,1,1 for what=scf_*, 9,1,1,1,1,1 for what=mur_lc_* and lmurn=.TRUE. or for cubic systems, 5 on all the relevant celldm parameters when lmurn=.FALSE. and the system is not cubic. step_ngeo(1),...,step_ngeo(6) : The step between the lattice constants at different geometries. step_ngeo(1) is, in atomic units, the change of a, step_ngeo(2), step_ngeo(3) are dimensionless and are the changes of the ratios b/a, c/a, step_ngeo(4), step_ngeo(5), step_ngeo(6) are the changes in degree of the angles alpha, beta, and gamma. The cosine of the angle is calculated by the program. Default: real 0.05 a.u., 0.02, 0.02, 0.5, 0.5, 0.5 lmurn : if .TRUE. the fit with an equation of state is done. Only ngeo(1) values of the energy are fitted, the other values of ngeo are not used. if .FALSE. use a quadratic or quartic function to interpolate the energy as a function of all celldm parameters. The number of self-consistent calculations is ngeo(1) x ngeo(2) x ngeo(3) x ngeo(4) x ngeo(5) x ngeo(6). In this case only the minimum energy and the optimal celldm are given in output. Default: .TRUE. ieos : choose the equation of state to use (only when lmurn=.TRUE.): 1 - Birch-Murnaghan third order 2 - Birch-Murnaghan fourth order 4 - Murnaghan Default: integer 4 show_fit : if .TRUE. show the contour plot of the fitted energy instead of the energy. Used by default when reduced_grid is .TRUE.. Default: logical .FALSE. frozen_ions: if .TRUE. the atomic coordinates are obtained by applying the strain to the coordinates given in the pw.x input to the new cell parameters (equivalent to keep the crystal coordinates fixed) and kept fixed. If .FALSE. the atomic coordinates are relaxed at each geometry. Default: logical .FALSE. vmin_input : minimum volume for the plot of the energy as a function of volume. Default: real 0.98 times the volume of the first geometry. vmax_input : maximum volume for the plot of the energy as a function of volume. Default: real 1.02 times the volume of the last geometry. deltav : distance between two volumes in the plot of the energy as a function of the volume. Default: real calculated from nvol. nvol : number of volumes in equation of state plot. Default: integer 51 lquartic : if .TRUE. fit the energy with a quartic polynomial. Default: logical .TRUE. lsolve : choose the algorithm used to fit the quartic polynomial parameters. Allowed values: 1 explicitly minimize chi^2 (usually less accurate than the other two. Should be used only for tests). 2 Use the QR algorithm to minimize chi^2 (lapack routine dgels) 3 Use the SVD algorithm to minimize chi^2 (lapack routine dgelss). Default: integer 2 flevdat : file where the equation of state is written. The results of the fit are then written in flevdat.ev.out. Default: character(len=*) 'output_ev.dat' flpsmur : postscript file of the equation of state plot. Default: character(len=*) 'output_mur' lel_free_energy : if .TRUE. computes the electronic thermodynamic properties (energy, free energy, entropy, and constant strain heat capacity) at each temperature and plots them. See the scf_dos option for the parameters that control the calculation. Default: .FALSE. ncontours : the number of contours in the energy plot. These levels can be determined automatically by the code or defined by the user. The energy levels can be defined after the INPUT_THERMO namelist but before the path, as a list: energy_level(1) color(1) ... energy_level(ncontours) color(ncontours) Color is a string of the type color_red, color_green, etc. The list of available colors is at the beginning of each gnuplot script. energy_level is in Ry units. Default: integer 9 do_scf_relax : if .TRUE. the code makes a self-consistent relax calculation at the equilibrium geometry to find the optimized atomic coordinates. This step is needed only for solids that have internal degrees of freedom in the unstrained configuration. If .FALSE. the coordinates of the input geometry are strained uniformly to the equilibrium geometry. Default: logical .FALSE. lgeo_from_file : if .TRUE. the input geometries are read from file. ngeo(1) must have the total number of geometries and lmurn must be .TRUE.. Default : .FALSE. lgeo_to_file : if .TRUE. at the end of the calculation the code writes in a file the geometries that correspond to the optimized crystal parameters for each value of celldm(1) of the grid of geometries. Default : .FALSE. flenergy : name of the file that contains the energy in a form that can be used by gnuplot to make contour plots. Default: character(len=*) 'output_energy' flgeom : name of the file that contains the geometries requested with the flags lgeo_to_file or lgeo_from_file. The file is in the directory energy files. Default: character(len=*) 'output_geometry' flpsenergy : file with the contour plots of the energy as a function of the crystal parameters. Default: character(len=*) 'output_energy'

An example for this option can be found in `example05`.

Number of tasks for this option:
`ngeo(1)` when `lmurn=.TRUE.`,
`ngeo(1)`
`x`
`ngeo(2)`
`x`
`ngeo(3)`
`x`
`ngeo(4)`
`x`
`ngeo(5)`
`x`
`ngeo(6)` when
`lmurn=.FALSE.`.