Hydrogen-helium interaction

Zhao Y, Lu G. QM/MM study of dislocation-hydrogen/helium interactions in a-Fe. Model. Simid. Mater. Sci. Eng. 2011 19 065004. 

Notwithstanding, after hydrogen, helium is also the simplest naturally available atomic species, which, in contrast to one electron atoms, exhibits the additional electron-electron interaction, as a source of electronic correlations. Hence, helium is one of the simplest systems where electronic correlations can be studied. Direct manifestations of electronic correlations have been found, e.g., in doubly excited states of helium localized along highly asymmetric, though very stable, frozen planet configurations (FPC) (K. Richter et.al., 1990), or scarred by... 

The list of simple atoms accessible now includes a broad range of very different natural and artificial systems hydrogen, helium, muonium, positronium, various few-electron ions, muonic atoms and exotic atomic systems containing a pion, antiproton etc. While hydrogen atoms form the essential part of our universe, the unstable atoms like muonium do not exist in nature at all. The investigation of simple atoms has provided us with important knowledge on fundamental interactions between the particles these atoms consist of. 

In the MNDO/d approach, the established MNDO formalism and parameters remain unchanged for hydrogen, helium, and the first-row elements. The inclusion of d orbitals for the heavier elements requires a generalized semiempirical treatment of the two-electron interactions. The two-center two-electrons integrals are calculated by an extension [33] of... 

A measurement of the density of helium gas shows that it is a monatomic gas. Molecules of He2 do not form. What difference between hydrogen atoms and helium atoms accounts for the absence of bonding for helium The answer to this question also must lie in the attractive and repulsive electrical interactions between two helium atoms when they approach each other. Figure 16-4A shows the attractive forces in one of our hypothetical instantaneous snapshots. There are, of course, four electrons and each is attracted to each nucleus. In Figure 16-4B we see the repulsive forces. Taking score, we find in Figure 16-4A eight attractive interactions, four... 

The parameters obtained here from measurements of B12 and Dn over wide ranges of temperature are probably as reliable as any that have been proposed for the interaction of molecules of different species. Unfortunately they do not provide an adequate test of Eqs. 9 and 10, since each of the systems has as one of its components either helium or hydrogen (for which there are significant quantum corrections) or carbon dioxide (which does... 

Exceptions are helium and hydrogen, which have very weak attractive interactions and relatively strong repulsive interactions at room temperature, they get warmer as they expand. 

As an example we may calculate the energy of the helium atom in its normal state (24). Neglecting the interaction of the two electrons, each electron is in a hydrogen-like orbit, represented by equation 6 the eigenfunction of the whole atom is then lt, (1) (2), where (1) and (2) signify the first and the second electron. 

Evidence has been advanced8 that the neutral helium molecule which gives rise to the helium bands is formed from one normal and one excited helium atom. Excitation of one atom leaves an unpaired Is electron which can then interact with the pair of Is electrons of the other atom to form a three-electron bond. The outer electron will not contribute very much to the bond forces, and will occupy any one of a large number of approximately hydrogen-like states, giving rise to a roughly hydrogenlike spectrum. The small influence of the outer electron is shown by the variation of the equilibrium intemuclear distance within only the narrow limits 1.05-1.13 A. for all of the more than 25 known states of the helium molecule. 

In Sections 42 and 43 we shall describe the accurate and reliable wave-mechanical treatments which have been given the hydrogen molecule-ion and hydrogen molecule. These treatments are necessarily rather complicated. In order to throw further light on the interactions involved in the formation of these molecules, we shall preface the accurate treatments by a discussion of various less exact treatments. The helium molecule-ion, He , will be treated in Section 44, followed in Section 45 by a general discussion of the properties of the one-electron bond, the electron-pair bond, and the three-electron bond. 

A hydrogen atom or a helium cation contains Just one electron, but nearly all other atoms and ions contain collections of electrons. In a multielectron atom, each electron affects the properties of all the other electrons. These electron-electron interactions make the orbital energies of eveiy element unique. 

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