Owing to the recent
developments in experimental techniques, the
number of crystal structures determined under various external stimuli
has considerably increased, giving the opportunity for specialized
data analysis. In this paper, the nonambient temperature and pressure
studies of crystals deposited in the Cambridge Structural Database
have been surveyed to better understand the relations between two
of the most fundamental properties of crystals, compressibility and
thermal expansion. Based on 799 systematic series of experiments,
a pressure–temperature correspondence rule was formulated,
stating that pressure between 0.2 and 0.5 GPa can be expected to cause
the same change of crystal volume as the temperature decrease from
300 to 100 K. The rule has been tested against a set of crystals undergoing
monotonic changes and no phase transitions in neither of the investigated
pressure or temperature ranges. Additionally, the changes of thermal
expansion and compressibility in the function of pressure and temperature
have been illustrated by the anisotropy-evolution plots. They demonstrate
limited applicability of Hazen and Finger’s rule of the inverse
relationship of pressure and temperature, particularly for metal–organic
crystals.