ABSTRACT
Until now we have discussed different effects of chemical significance on the
basis of considering quantities related to the different type of densities. Now
we shall turn to energetic effects-they are of utmost importance for chem-
istry: the energy of the system is crucial for all phenomena-from molecular
geometry to the dynamics of the reactions. However, the total energy is only
a single number; one has to understand the factors governing its changes un-
der different circumstances. We know that there are quite similar bonds and
groups in different molecules, indicating that there are similar energetic ef-
fects in them. Our task is to identify and utilize these local parameters: the
understanding and interpretation of the results obtained in a quantum chemi-
cal calculation can be much facilitated by presenting the total energy as a sum
of chemically meaningful components.
