Energy and density analyses of the H2 molecule from the united atom to dissociation: The ∑1g+ states

Abstract

The first 15 (1)Sigma(g)(+) states of the H(2) molecule are computed with full configuration interaction (CI) both from Hartree-Fock molecular orbitals and Heitler-London atomic orbitals; the computations are correlated with a comprehensive analysis. The basis sets utilized are extended and optimized Slater-type functions [Slater-type orbital (STO)] and spherical Gaussian functions [Gaussian-type orbital (GTO)]. The full CI computations cover the internuclear distances from 0.01 to 10,000 bohr. The available accurate data by Wolniewicz and co-workers for the first five excited states verify the quality of our computations. We focus on the characterization of the orbitals in the wave functions, on the electronic density evolution from the united atom to dissociation, on quantitative decomposition of the total energy into covalent and ionic components, and on detailed analyses of energy contributions to the total state energy from selected STO and GTO subsets. These analyses lead to study (with full CI) the H(-) negative ion with a proton and the H(+)H(-) ion pair systems. The ground and excited states for the He and H atoms and for the H(-) ion are computed to discuss the united atom and the dissociation products H(1s)+H(nl) of the n state manifolds. With the exception of n=1, each manifold has one state, specifically the EF, H, 7, and 11, whose second minimum has strong ionic character; state 11 dissociates as H(+)H(-).

Adiabatic potential-energy curves of long-range Rydberg molecules: Two-electronR-matrix approach

“…is in excellent agreement with the previously published results of the ab initio quantum chemical calculations by Staszewska and Wolniewicz [44]. Moreover, the results of Corongiu and Clementi [43] for higher energies are also in good agreement with the findings presented here.…”

“…In order to test the basic mechanisms of the method we decided to test it on the simplest of molecules, H 2 . Present results accurately reproduce previous ab initio calculations [43,44] for lower states (n = 3, 4) and they predict yet undocumented oscillatory character of higher anti-bonding states H(1s) + H(nl). While these oscillations are also well reproduced by the two contact-potential models tested in this paper, the absolute energies predicted by the contact-potential models are systematically lower than the more accurate two-particle calculations.…”

“…The accuracy of the ion-pair PEC is sensitive predominately to the quality of the represen- Clementi [43], the points denoted by + in the lower inset are the energies calculated by Staszewska and Wolniewicz [44].…”

“…This term becomes important because larger variation of the potential V B around the perturber provides the scattered electron with higher local momenta via Eq. (43). In fact, we also carried out tests (not published here)…”

On stability and protonation of multielectron systems: The concept of proton affinity. II. Dissociative proton attachment and protonation—Deprotonation mapping

“…The ZPE-corrected PA(He) ¼ 42.5 kcal mol À1 ($1.9 eV) [29,32] is the smallest known PA. Note, closing this Section that H 2 can also be treated as H þ | H À [33]. 4 The archetypal example of multiprotonation is that of benzene (see Ref.…”