Features of contraction of solids: cooling vs pressing

Contraction of solid elements and compounds by cooling from room temperature to 0 K or by mechanical pressing to the same volume at 298 K is experimentally determined. We found that the energy cost of cold compression exceeds the energy of mechanical compression on average by two orders of magnitude. This fact is caused by the different mechanisms of contraction: pressing directly reduces interatomic distances, cooling mainly reduces the amplitudes of harmonic vibrations of atoms, whereas the anharmonic part of the vibration energy, responsible for the thermal contraction, is very small, ca. 1%.