The present volume gathers a series of selected and updated contributions presented at the International Symposium on Applied Theoretical Chemistry held in Havana, Cuba, July 2-6, 1990. This Symposium was intended to illustrate current applications of Theoretical Chemistry in different fields of Physical Chemistry. Theoretical Chemistry has become a powerful tool of investigation in all areas of Chemistry, Biochemistry, and Physical Chemistry. The plenary lectures given in the Symposium were classified into four topics: Atom-Surface Interactions, Chemical Reaction Mechanisms, Molecular...