Theoretical Study for Potential Energy Curves, Dissociation Energy and Molecular Properties for (LiH, H₂, HF) Molecules

Abstract

ABSTRACT.A theoretical study has been carried out of calculating dissociation energies and potential energy curves (Deng-Fan potential and Varshni potential) and molecular parameters of of ground state of diatomic molecules (LiH, H 2 , HF). Dissociation energies and potential energy curves depended on spectroscopic constants (ω e , ω e x e , r e , α, µ, β , ) and our results has been compared with experimental results. Molecular and electronic properties as ε HOMO , ε LUMO, ionization potentials (IP), electron affinities (EA) and binding energy was performed by using B3P86/6-311++g** method and Gaussian program 03, the results is well in a agreement with that of other researchers. INTRODUCTIONA potential energy curve is a graphical representation of the change in potential energy of the molecule as a function of the distortion of the bond of the molecule from its equilibrium distance. The knowledge of potential energy curves is of prime importance in the study of diatomic molecular spectra [1]. In the calculations of Franck Condon factor, dissociation energy and thermodynamic quantities etc, the studies of potential energy carves are necessary. The empirical potential energy functions like Varshni [2] and Deng-Fan potential [3] are usually applied and the potential energy carves are drawn. Naturally to compute the turning points of various vibrational levels the accurate spectroscopic constants are required. The empirical potential energy functions also require these molecular constants.Lithium hydride, the simplest stable metallic hydride, and the subject of an extensive review in 1993, continues to generate intense theoretical and spectroscopic interest. In particular, it provides a testing ground for new techniques, permits validation of approximate methods, and the existence of various isotopes allows analysis of the breakdown of the Born-Oppenheimer (BO) approximation. Of additional interest are the mutual neutralization of Li + and H − ions.[4] Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds. HF is widely used in the petrochemical industry and is a component of many super acids. Hydrogen fluoride boils just below room temperature whereas the other hydrogen halides condense at much lower temperatures. Unlike the other hydrogen halides, HF is lighter than air and diffuses relatively quickly through porous substances. Hydrogen fluoride is a highly dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with tissue. The gas can also cause blindness by rapid destruction of the corneas [5,6].Theoretical determination of the dissociation energy of the simplest, prototypical chemical bond in the hydrogen molecule has a long history. It started in 1927, very shortly after the discovery of quantum mechanics, by the work of Heitler and London [7] who approximately solved the Schrödinger equation for two electrons ...