within the molecules, it must be kept in mind that intermolecular distances are usually compressed first when applying pressure, due to the higher compressibility of these "soft" degrees of freedom. There is a great diversity of intermolecular interactions, e.g., coulombic and van-der-Waals interactions and hydrogen bonds, and each type of interaction responds to pressure differently. Therefore, depending on the chemical system under consideration, strengthening intermolecular interactions between functional groups by pressure may either be stabilizing or possibly precondition the molecules for polymerization. In the case of hydrogen cyanide (HCN) chains, a mixed PBC, X-HCFF and GOSTSHYP study using DFT showed that the pressure-induced strengthening of the interaction between the nitrogen lone electron pair and the carbon-hydrogen σ * orbital leads to a lengthening of the carbon-hydrogen bond. As can be seen from these examples, pressure-induced changes in electronic configurations, atomic radii, chemical bonds and atomic/molecular properties are diverse and, in many cases, system-specific.