23 How do I calculate the elastic constants as a function of temperature?

This is a two step calculation. First use what='elastic_constants_t'. This option computes the elastic constants for all the geometries used by what='mur_lc_t'. Then copy the directory elastic_constants in a new directory and with the same input for pw.x, run again thermo_pw using what='mur_lc_t'. Presently the code computes the temperature dependent elastic constants only within the ``quasi-static'' approximation, meaning that it interpolates the elastic constants found in the first step at the geometry that minimizes the Helmholtz (or Gibbs at finite pressure) free energy. The plot of the elastic constants will be found in output_ahar.el_cons.ps. Note that this approach used with the option lmurn=.FALSE. can calculate the thermodynamic properties of non-cubic solids.