SC-MEH MO calculations on H{sub 3}{sup -}

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:171902

Boudreaux, E A; Ferry, D J ^[1]

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1. Univ. of New Orleans, LA (United States)

The Self Consistent Modified Extended Huckel (SC-MEH MO) method has been applied to the H{sub 3}{sup -} ion. Attempts to treat the problem as an independent atom cluster of H+ H+ H-, with H-H and H---H{sup -}distances of 0.74 and 2.05 angstroms respectively, were unsuccessful. Even the inclusion of 2s, 2p polarization functions did not improve the situation, which invariably resulted in a large stabilization energy with abnormally high atomic charges. However, when the MO`s of the H{sub 2} molecules from an initial calculation were employed as the starting basis to be combined with the H{sup -} A.O. functions, the results obtained were quite satisfactory. Because of significant polarization in H{sup -} as noted earlier the A.O. basis was taken at the 1s, 2s, 2p. But extension of the H{sub 2} basis to include the 2s and 2p levels led to very poor results, as the overlaps were enormous at 2.05 {angstrom} ---H{sup -}distance. Thus, the H{sub 2} MO basis was confined to the 1s and *1s levels. Overlapped-matched STOs were employed for all AO functions. The results obtained for H{sub 3}{sup -} with singlet ground state are presented. There are several important points to be noted. The HOMO(2{sigma}) is 99.76 percent H{sup -} character, while the next bonding level which is some 6.3 eV lower in energy, is 87 percent H{sub 2}. Thus the degree of covalent bonding between H{sub 2} and H{sup -} is slight. The involvement of the 2s and 2p levels, though small, in the bonding MO`s, is not negligible. This is of particular significance in the LUMO(3{sigma}), which is only some 0.49 ev above the HOMO, and is 70 and 30 percent 2s and 2p character respectively.

• OSTI ID: 171902
• Report Number(s): CONF-9411143--
• Country of Publication: United States
• Language: English

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