4.2 Coordinates and structure

The thermo_pw code requires the Bravais lattice of the solid. Moreover for computing some quantities it assumes that the direct lattice vectors are those provided by the routine latgen.f90 of the QUANTUM ESPRESSO distribution. For this reason it is not recommended to use ibrav=0 in the pw.x input. The preferred method is to give the value of ibrav using primitive vectors provided by QUANTUM ESPRESSO. It is also possible to specify the space_group number and the coordinates of the nonequivalent atoms. When the pw.x input contains the ibrav=0 option, thermo_pw writes on output the values of ibrav, celldm, and of the atomic coordinates that should be used in the input of pw.x to simulate the same solid and stops. There are however two input variables of thermo_pw that can modify this behavior:

continue_zero_ibrav : when ibrav=0 in the input of pw.x and this variable 
             is set to .TRUE. thermo_pw runs with ibrav=0 (not recommended
             except when you deal with a supercell). 
             When this variable is .FALSE. and ibrav=0 the behavior 
             depends on find_ibrav.
             Default : logical .FALSE.

find_ibrav : This variable is active only when continue_zero_ibrav=.FALSE..
             When this variable is set to .TRUE. and the input of pw.x
             has ibrav=0, thermo_pw finds the values of ibrav, celldm,
             and of the atomic positions that produce the same crystal 
             and continue the calculation. The geometry 
             used by thermo_pw might be rotated with respect to the input and
             have different primitive vectors.
             When this variable is .FALSE. the code stops after writing in
             output ibrav, celldm, and the atomic positions. These variables 
             can be copied in the pw.x input. Note that the automatic 
             identification of the lattice does not work for supercells.
             Default : logical .FALSE.