1.32 How do I calculate the piezoelectric tensor for each geometry?

To compute the piezoelectric tensor across various geometries, set what='piezoelectric_tensor_geo'. When this option is active, the code performs the following steps: It uses the equilibrium geometries previously identified by what='mur_lc' as a baseline to generate a set of distorted configurations. It computes the Berry phase for each distorted structure and it calculates the piezoelectric tensor for every equilibrium geometry. The resulting files are saved in the elastic_constants/ directory. If you want to account for internal coordinate relaxation using FFEM, you can refine the calculation with additional variables. Use stypec, iconstr_internal_ec, and nint_var_ec (refer to the User’s Manual for specific mapping values) and set the flag use_free_energy=.TRUE.. This workflow produces a piezoelectric tensor where internal coordinates are optimized via FFEM after strain. These files are saved in the anhar_files directory and are ready to be interpolated across your temperature (and/or pressure) range.