화학공학소재연구정보센터
Journal of Chemical Physics, Vol.101, No.9, 7782-7787, 1994
Ab-Initio Calculation of Vibration Frequencies, Infrared Intensities, and Structures for H-4(+), Lih3+, Li2H2+, and Li-4(+), and Deuterated Analogs
The six normal mode vibration frequencies and infrared intensities for H-4(+) and three tetra-atomic lithium-hydrogen ion clusters have been calculated using ab initio SCE MP2, and CISD methods. Vibration frequencies are also reported for all possible deuterated analogs of the four ions. The normal mode vibrational characteristics and structures of the ions are discussed and compared to each other. The H-4(+) ion can reasonably be regarded as a strongly bonded, triangular H-3(+) core with an additional H atom less strongly bound to one of the ring hydrogens in a planar C-2v arrangement. The calculated normal mode vibration frequencies for H-4(+) and its deuterated analogs confirm this picture. The hydrogen-lithium clusters, LiH3+, Li2H2+, and Li-4(+), had structures and normal mode frequencies which did not yield the same ring/ligand picture as H-4(+), Instead, these ions behaved like two interacting diatomic fragments (e.g., H-2 and LiH+ subunits in LiH3+) oriented perpendicular to each other in a planar arrangement. The potential energy surfaces for the hydrogen-lithium cluster ions displayed two extremely low frequency vibrational modes corresponding to angular motion of these diatomic subunits relative to each other.