In order to make a calculation with thermo_pw you need to be able to produce an input file for the pw.x code of QUANTUM ESPRESSO. This input file requires mainly five information:
The Bravais lattice is specified by an integer number ibrav and by the crystal parameters celldm (up to six numbers). You can find information on the ibrav code and on the required crystal parameters in the file PW/Doc/INPUT_PW of the QUANTUM ESPRESSO distribution. In QUANTUM ESPRESSO you can use ibrav=0 and give the primitive lattice vectors of the Bravais lattice. Presently thermo_pw needs to known the Bravais lattice number so this form of input is not recommended. If you use it, thermo_pw writes on output the ibrav, the celldm and the atomic coordinates needed to simulate the same cell and stops. You can therefore just cut and paste ibrav, celldm and the atomic coordinates in the input of pw.x. Alternatively you can set the flag find_ibrav=.TRUE. in the thermo_pw input and thermo_pw will make the conversion for you and run the job. After setting the correct ibrav and celldm, thermo_pw might still tell you that the Bravais lattice is not compatible with the point group. This can happen, for instance, if you have isolated molecules, amorphous solids, or defects. In these cases you can still continue but symmetry will not be used to reduce the number of components of the tensors that represent the physical quantities. In order to use the residual symmetry, you have to use one of the suggested ibrav, adjusting the celldm to the parameters of your cell. For instance if you have a cubic cell, but the symmetry requires a tetragonal lattice, you have to use a tetragonal lattice with celldm(3)=1.0. In rare cases, with lattices such as the face-centered orthorhombic some symmetry operations might be incompatible with the FFT grid found by pw.x. The choice made in QUANTUM ESPRESSO is to discard these symmetries making the lattice incompatible with the point group. In these cases the code needs nr1=nr2=nr3. Set these three parameters in the pw.x input equal to the largest one.
The positions of the atoms inside the unit cell are defined by an integer
number nat (the number of atoms) and by nat
three-dimensional vectors as specified in the file PW/Doc/INPUT_PW.
You can use several units, specify the coordinates in Cartesian or on the
crystal basis or you can give the space group number and the
coordinates of the inequivalent atoms.
These options are supported by thermo_pw. See the pw.x manual
for details.
The number of different types of atoms is given by an integer number
ntyp and for each atomic type you need to specify a
pseudopotential file. Pseudopotential files depend on the exchange and
correlation functional and can be found in many
different places. There is a pseudopotential page in the QUANTUM ESPRESSO website, or
you can consider generating your pseudopotentials with the pslibrary
inputs. You can consult the web page http://www.qe-forge.org/gf/project/pslibrary/ for more information.
The kinetic energies cut-offs depend on the pseudopotentials
and on the accuracy of your calculation. You can
find some hints about the required cut-offs inside the pseudopotentials files,
but you need to check the convergence of your results with the cut-off
energies.
The k-point mesh is given by three integer numbers and possible
shifts (0 or 1) in the three directions. The convergence of the results
with this mesh should be tested.
Once you have an input for pw.x, in order to run thermo_pw you have to write a file called thermo_control that contains a single namelist called INPUT_THERMO. This namelist contains a keyword what that controls the type of calculation performed by thermo_pw. Ideally you should set only what and make a calculation similar to pw.x calling instead the executable thermo_pw.x and giving as input the input prepared for pw.x.