  The spatial distribution of the internal pressure of an electron fluid, which
spontaneously arises at the formation of a molecule or a crystal, is linked to
the main features of chemical bonding in molecular crystals. The local pressure
is approximately expressed in terms of the experimental electron density and
its derivatives using the density functional formalism and is applied to
identify the bonding features in benzene, formamide and chromium hexacarbonyl.
We established how the spatial regions of compression and stretching of the
electron fluid in these solids reflect the typical features of chemical bonds
of different types. Thus, the internal electronic pressure can serve as a
bonding descriptor, which has a clear physical meaning and reveals the specific
features of variety of the chemical bonds expressing them in terms of the
electron density.
