Molecular structure and properties of some linear molecules - a study of post Hartree-Fock and density functional theory

We have chosen a few linear molecules [NCCCX, X = H, F, Cl, Br; FCCH, FCCF, ClCCCl], containing electronegative atoms to study the structure and properties of these molecules by using a higher level of DFT and ab initio methods. The molecular geometries were optimized employing the atomic basis sets 6-311++G(2d,2p), 6-311++G(3df,3pd) in BLYP, B3LYP, BP86 level of theory of DFT and 6-13G* basis set at MP2 level of theory in the ab initio method. The optimized structural parameters and other properties of the molecules obtained by the post-Hartree-Fock and DFT methods are discussed with experimental values. Density functional theory parameters chemical hardness and chemical potential were calculated employing the atomic basis set 6-13G* at the MP2 level of theory in the ab initio method. These parameters were discussed in relation to the electronegativity of the atoms. (C) 1999 Elsevier Science B.V. All rights reserved.