Melting Temperature Under Pressure in ‘Hard’ and Soft Matter

This report focuses on cognitive gaps for pressure dependence of the melting temperature, presenting: (i) the coherent discussion on T_m (P) behaviour both for ‘Hard’ Matter (‘standard’ solid state) and Soft Matter systems, to reveal the importance of intermolecular interactions strength, (ii) the model picture linking systems with (dT_m)⁄(dP>0), (dT_m)⁄(dP< 0) and T_m (P) curve maximum; which also shows the relevance of the negative pressures domain, (iii) the ultimate validation test of the recent ‘universal’ scaling of T_m (P) pattern derived by Trachenko [Phys. Rev. E 2024, 109, 034122] against empirical data. The evidence for ‘Hard Matter’ focuses on systems relevant for the semiconductor industry, but yet under-discussed: Silicon, Germanium, and Gallium Nitride. For Soft Matter, these include unique polymeric systems and liquid-crystalline pentylcyanobiphenyl (5CB). For the latter, symmetry-selected melting/freezing takes place. Finally, the specific case of graphite and diamond a discussed. The report includes an innovative solution for melting temperature under-pressure detection.