Diatomic And Triatomic Molecules Of The Transition Elements Of The Ground State Properties

The equilibrium bond lengths, harmonic vibrational frequencies, and dissociation energies of the ground state homonuclear 3d transition-metal diatomics Sc2,Ti2,V2,Cr2,Mn2,Fe2,Co2,Ni2 and Cu2 were determined using three density functional theory methods(BLYP,B3LYP and B3P86) and two all electron basis sets(DGDZVP and TZVP). Results are compared to other theoretical studies and to experimental values when available. The accuracy of the DFT results is found to be highly dependent upon the functional employed, with the pure DFT methods, BLYP performing significantly better than the hybrid HF/DFT methods. For Co2 cluster, the B3LYP and B3P86 methods can not predict the equilibrium bond length, harmonic vibrational frequencie, and dissociation energie. For the van der Waals complex Mn2, all the functionals predict the ground state to be high-spin. This study provides a challenge for new experimental and theoretical studies of the transition-metal diatomics and new experiments are sorely needed. In addition, we encourage future theoretical studies to examine all nine transition-metal diatomics at consistent levels of theory. Only in this way will a broad picture of the reliability of the theory emerge.Density-functional theory has been used to determine the ground-state geometries and electronic states for homonuclear transition-metal trimers(Sc3,Ti3,V3,Cr3,Mn3,Fe3,Co3,Ni3 and Cu3)constrained to equilateral triangle geometries. One of the primary goals of the present research was to obtain consistent theoretical results for all of the transition-metal trimers, so that comparisons can be safely made. First, it is important to note the ground-state spin multiplicities. Going from left to right from scandium, these BLYP multiplicities are seemingly somewhat haphazard:2,5,2,7,16,11,8,3,2。To a certain extent, the multiplicities can be expected to represent the degree of bonding of the molecule, and this structure should be reflected in the bond lengths and binding energies; this hypothesis only proves partially true. Equilibrium bond lengths fall monotonically from the scandium trimer to the chromium trimer, despite the fact that the chromium trimer has a much higher spin. However, from manganese trimer to the copper trimer, the manganese trimer not only has the highest multiplicity 11, but also has the longest bond length 2.810A.Secondly, the Jahn-Teller effect is an important matter for transition-metal clusters. Reserch shows that Sc3 Mn3 and Ni3 do not have Jahn-Teller effect, they are standard equilateral triangle structures. But Ti3,V3,Fe3,Co3å'ŒCu3 have different extent Jahn-Teller effect. First find that Cr3 has the biggest Jahn-Teller effect, the ground-state geometric structure close to the right triangle. This structure needs further research.