In this section, we apply our findings from Section 2.4 to study the combined effects of different experimental conditions on the polymorphism. It is instructive to consider the case without an electric field (F = 0 V nm -1 ) first, i.e., to only vary pressure and temperature. In earlier work, Egger et al. provided a pressure-temperature phase diagram in the Supporting Information that shows the most stable category (lying/standing) for different pressures and temperatures. To reproduce this phase diagram and extend it to different electric fields, we predicted the energies for different fields using the SAMPLE approach. This is done by training energy models with band structure calculations of 200 to 300 different polymorphs (all details in the Supporting Information). Separate energy models were trained for all external electric fields between -3 V nm -1 and +3 V nm -1 .