Covalent interaction and semiempirical modeling of small molecules

The use of sophisticated methods for modeling complex systems is gaining ever more importance recently because they allow the design of material with properties tailored to specific applications. However, problems may arise from conflicts between different reaction pathways inherent in the wide variety of chemical elements used. This is reflected by the impossibility of exactly solving the Schroedinger equation or of exactly describing the exchange interaction in density functional theory when the system complexity increases. An alternative is offered by the application of semiempirical methods because they strongly reduce system complexity. Normally, this is accomplished by increasing the degree of the approximations to the detriment of the formalism generality. This work is aimed to improve the semiempirical electronegativity equalization method. This is accomplished by modifying the point charge Madelung potential with the introduction of covalent interaction to better describe the chemical bonds.