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 prope rties of these molecules by using a higher level of DFT and ab initio metho ds. 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. T he optimized structural parameters and other properties of the molecules ob tained by the post-Hartree-Fock and DFT methods are discussed with experime ntal values. Density functional theory parameters chemical hardness and che mical potential were calculated employing the atomic basis set 6-13G* at th e MP2 level of theory in the ab initio method. These parameters were discus sed in relation to the electronegativity of the atoms. (C) 1999 Elsevier Sc ience B.V. All rights reserved.