Theoretical study on the molecular structures of nitrophenols and trinitrophenols

Computational quantum chemistry is the ground of molecular modeling, on prediction the behavior of individual molecules within a chemical system. The basis of molecular modeling investigations is quantum mechanics, but in order to achieve quantitative results comparable with experimental we need supercomputer's power or parallel computers cluster. Such way is very useful with explosive materials that require exceptionally care in their handling. The theoretical investigations of molecular electronic structure and geometrical data of 2, 4, 6-trinitrophenol and five positional nitro phenol isomers were performed applying of ab initio, quantum mechanical methods using the GAMESS computer code integrated under the SCore type PC cluster TAURAS [1, 2]. Was used Hartree-Fock approximation with 6-31G* basis set (polarization d functions on second period elements; all in all 250 basis functions). Also 6-311G** basis set with two polarization d functions on second period elements, and plus one f function and diffuse s and p functions on second period atoms, and additionally diffuse functions on hydrogen atoms (all in all 770 basis functions). The basis functions used are necessary to achieve reliable results in such investigations. Calculated geometrical parameters were compared and found to be in good agreement with the data of X-ray diffraction. The nitro phenol molecular structure was affected by the position of the NO2 group. All calculations were made on the local area PC cluster TAURAS with the SCore cluster system software. Obtained results show that the cluster is good device for such tasks.