ABSTRACT
The potential energy surface of Zn n O n clusters (n = 2, 4, 6, 8) has been explored by using a simulated annealing method. For n = 2, 4, and 6, the CCSD(T)/TZP method was used as the reference, and from here it is shown that the M06-2X/TZP method gives the lowest deviations over PBE, PBE0, B3LYP, M06, and MP2 methods. Thus, with the M06-2X method we predict isomers of Zn n O n clusters, which coincide with some isomers reported previously. By using the atoms in molecules analysis, possible contacts between Zn and O atoms were found for all structures studied in this article. The bond paths involved in several clusters suggest that Zn n O n clusters can be obtained from the zincite (ZnO crystal), such an observation was confirmed for clusters with n = 2 - 9,18 and 20. The structure with n = 23 was obtained by the procedure presented here, from crystal information, which could be important to confirm experimental data delivered for n = 18 and 23.
ABSTRACT
The theoretical study of the interaction between CH(2) and fullerene (C(60)) suggests the existence of an addition reaction mechanism; this feature is studied by applying an analysis of electronic properties. Several different effects are evident in this interaction as a consequence of the particular electronic transfer which occurs during the procedure. The addition or insertion of the methylene group results in a process, where the inclusion of CH(2) into a fullerene bond produces the formation of several geometric deformations. A simulation of these procedures was carried out, taking advantage of the dynamic semi-classical Born-Oppenheimer approximation. Dynamic aspects were analyzed at different speeds, for the interaction between the CH(2) group and the two bonds: CC (6, 6) and CC (6, 5) respectively on the fullerene (C(60)) rings. All calculations which involved electrons employed DFT as well as exchange and functional correlation. The results indicate a tendency for the CH(2) fragment to attack the CC (6, 5) bond.
Subject(s)
Fullerenes/chemistry , Methane/analogs & derivatives , Electrons , Ions , Methane/chemistry , Models, Chemical , Models, Molecular , Models, Theoretical , Quantum Theory , ThermodynamicsABSTRACT
The interaction between alcohol molecules and platinum (Pt) was studied using molecular dynamics (MD; Born-Oppenheimer method). Alcohol molecules like ethanol and methanol present a similar molecular structure, with a methyl group (CH(3)) at one end and a fragment of hydroxyl (OH) at the other. This fact generates two orientations that are considered in the interaction with Pt. The MD calculation results for these two orientations indicate a preferential orientation due to energy interactions. A plausible reaction mechanism that takes into account the interaction between Pt and alcohol is presented. The charge transference obtained from the Pt-alcohol interaction was also analyzed. The energy for the two orientations was calculated by indicating the preferential orientation. The methyl and hydroxyl groups are involved in heterolytic breakage of hydrogen bonds, joined to a carbon atom in the former and to an oxygen atom in the latter; however, the methyl group reaction seems to be the most important.
Subject(s)
Ethanol/chemistry , Methanol/chemistry , Models, Chemical , Platinum/chemistry , Computer Simulation , Quantum Theory , ThermodynamicsABSTRACT
Aromatic rings can suffer severe distortions upon substituting transition metal centers with certain kinds of organometallic compounds. This property is very interesting because aromaticity can remain despite the deformation. Theoretical calculations at the density functional theory level were carried out on two such structures containing vanadium and iron centres [(C5H5-V-H)(2)C6H6 and (CpFe)(2)C6(CH3)(6)] in order to analyze the nature of the bonds as well as the magnitude of the prevalent aromaticity and how this depends on the electronic characteristics around each metal atom. The analysis of aromaticity was carried out on the basis of known methods, such as HOMA and FLU, with consistent results. The results also show features that suggest a possible catalytic behavior of the species under study.
