Theoretical Study On The Structure And Structure Distortions Of Some Binary Clusters In Carbon And Nitrogen Family

Ten new clusters of C₅P₃₀(D₅), Si₅P₃₀(D₅), Si₆P₃₆(D_6h), C₆P₃₆(D₆), C₁₀N₄₀(D_5d), C₁₅N₅₀(D_5h) and C_nN_2n(n=2-5)(D_nh) were predicted theoretically to be stable by geometry optimization and vibrational frequency confirmation via density functional theory (DFT) approaches. Thermo-chemical properties such as enthalpies of formation were predicted at different theoretical levels.B3PW91/6-31G density functional calculations were performed on the potential energy curves (PECs) of C₅N₃₀(D_5h), C₅P₃₀(D₅), Si₅P₃₀(D₅), Si₆P₃₆(D_6h) and C₆P₃₆(D₆) cage clusters from structure distortions realized by modification of redundant coordinates. The over-all elastic (force) constants k were therefore calculated by pure conic fits of the PECs for displacements close to equilibrium structures. PECs had also been accurately fitted into polynomials analytically for large structure distortions with the correlation coefficients R generally great than 0.99998. The strength (the maximum energy necessary for destroying the structure) in different independent directions for each of the clusters was predicted from the PECs. In addition, this work also carried out time-dependent (TD) DFT analysis on the vertical low lying electronic excitation energies for all of the distortions at B3PW91/6-31G level.For the tubic clusters of C₁₀N₄₀, C₁₅N₅₀, the vertical low lying electronic excitation energies were calculated by TD DFT at B3PW91/6-31G* level.For C_nN_2n(n=2-5) clusters, the properties were studied in detail. The vertical low lying electronic excitation energies were calculated by TD DFT at B3PW91/6-31G* level. The enthalpies of formation as well as dissociation energies, adiabatic and vertical ionization energies, electron affinities and combustion enthalpies were predicted quantitatively by accurate model chemistry at G3MP2 level.