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Floating spherical gaussian orbital open‐shell calculations on the four‐electron H 4 system
Author(s) -
Huang Hsing Hua,
Pakiari Ali H.
Publication year - 1977
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560120402
Subject(s) - open shell , atomic physics , saddle point , electron , chemistry , planar , potential energy , physics , molecular physics , geometry , quantum mechanics , mathematics , computer graphics (images) , computer science
Floating spherical Gaussian orbital ( FSGO ) open‐shell calculations have been made to determine the potential energy surface of planar square and rectangular arrangements of the four‐electron system H 4 . This surface is discussed in relation to the bimolecular isotope exchange reaction H2+D2‐→ 2HD. The changes in energy and geometry accompanying the coplanar approach of two hydrogen molecules interacting chemically have also been investigated. Calculations on the electronic energies of planar T‐shaped and kite arrangements of H4 of various sizes show that it is unlikely that these configurations can serve as transition states for the exchange reaction. However, the energy curve for linear configurations of H4 (HHH … H), calculated as a function of the H 3 … H distance with the symmetric linear H 3 (H‐H‐H) unit fixed at the internuclear distance of 1.9080 a.u., is found to have a deep minimum (−1.9176 a.u.) at an r (H 3 … H) distance of 1.5846 a.u. The overall results suggest that the following mechanism for the exchange reaction, H 2 +H 2 →H 2 +H+H→H 3 +H→H+H 2 + H→H 2 +H 2 could be advantageous as it requires a barrier height of 0.1604 a.u. which is significantly lower than that calculated from the saddle point energy (0.1950 a.u.). However, the problem of reconciling this with the experimental activation energy of 0.0685 a.u. still remains.