LCAO–MO–SCF Calculations Using Gaussian Basis Functions. IX. Possible Rare Gas Adducts with Beryllium Species, HeBeH2 and BeHe

Abstract

As a result of the extreme electron deficiency of the Be in BeH2 (only 3.3 electrons instead of the 4.0 in the neutral Be atom), it should be possible to prepare novel complexes of beryllium hydride such as its rare gas adducts. As an initial study we performed ab initio LCAO–MO–SCF investigations using Gaussian basis functions of the helium adduct of beryllium hydride, HeBeH2. The calculated energy results showed this species to be marginally unstable with respect to He+BeH2 (in many different geometrical configurations). However, the population analysis results do indicate a slight propensity to binding between the He and the Be. The gross atomic populations indicate a slight shift of electron density from the He to the Be and the He–Be total overlap population is positive, again indicative of an incipient bond. For comparison the BeHe system itself was subjected to a similar theoretical treatment. The energy results show there to be considerably less repulsion energy between He and BeH2 than between He and the isolated Be atom. (This behavior would be expected commensurate with the greater electron deficiency of Be in BeH2 than in the isolated Be atom.) The same phenomenon is reflected in the positive He–Be total overlap population as a function of distance for HeBeH2 as contrasted with a negative He–Be total overlap population in BeHe at the same distances. (The repulsive curve for BeHe itself also implies that species such as BeHe, BeHe2, or BeHe3 will not be preparable, contrary to recent proposals by experimentalists.) Thus while HeBeH2 appears not to be a promising species it is postulated that the higher rare gas complexes will be more stable. We conjecture that it should be possible to make and perhaps even to isolate the xenon complex of BeH2. It should be emphasized that any scattering data of rare gases, even He, should be analyzed taking into account the short range chemical type forces which our LCAO–MO–SCF calculations have demonstrated to exist between rare gases and molecules. Our results imply that even He is not inert and any experiments using carrier gases should be considered very carefully in this context.