Potential Energy Surfaces for LiH₂ and Photochemical Reactions Li*+ H₂ ↔ LiH + H

Abstract

Potential energy surfaces for the Li*+ H2 → LiH + H and the reverse reactions are calculated using ab initio methods. Extensive configuration interactions have been done for a large number of collinear, C 2 v , and C s geometrical forms using a large basis set to describe the 2s−3d atomic states of the lithium atom and the neutral and anionic hydrogen molecule. The Li(3s) channel has a small activation barrier and leads to a stable intermediate, 4 2A‘ (LiH2)*, but a diabatic coupling between the 3 and 4 2A‘ surfaces would preferentially lead to a nonreactive inelastic collision producing Li(2p). The Li(2p) channel leads to one entirely repulsive potential surface (3 2A‘) and two attractive potential surfaces (2 2A‘ and 1 2A‘ ‘) resulting in two stable intermediates. The Li(2p) atoms with enough collision energy to overcome the endothermicity of 1624 cm-1 can lead to the reaction producing LiH. Those three excited intermediate complexes are bent (planar) and not linear. The charge transfer from the metal atom to the hydrogen molecule does not occur in the course of the collision but much later, when one hydrogen atom breaks away, implying that the harpooning model does not apply to this case. The reverse reaction LiH + H → Li + H2 can produce (i) the high-energy Li(2s) directly, (ii) the thermal Li(2p), and (iii) the thermal Li(2s) accompanied with a chemiluminescence. The 2 2A‘ intermediate may play an important role in the reverse reaction, too.

Investigation of Stereo-dynamic Properties for the Reaction H+HLi by Quasi-classical Trajectory Approach

“…they also reported that there is a small barrier with the height of about 0.04 eV. After a short time, Lee et al 4 reported a new ground state PES which shows a downhill descending shape from the initial state H+HLi to the final state H 2 +Li, and they found that 1 2 A' intermediate plays an important role in the reaction process. Dunne et al 5 derived an analytical potential energy surface named DMJ PES by fitting a many-body potential to energies obtained from high quality ab initio (CI) calculations and carried out the reaction cross sections for reaction H+HLi → H 2 +Li at various collision energies and selected rotational states.…”

“…[3][4][5][6][7][8][9][10][11][12][13] The pioneer work can be traced to Clarke et al, 3 where they firstly calculated the adiabatic LiH 2 potential energy surface using the spin-coupled valence bond (SCVB) non-orthogonal configuration interaction (CI) method, and found that cold LiH molecules can be depleted by reactive encounters with H atom at low collision energy. they also reported that there is a small barrier with the height of about 0.04 eV.…”

Coriolis Coupling Influence on the H+LiH Reaction

“…[11][12][13][14] The LiH 2 chemical system has been the subject of a large number of studies on its potential energy surfaces (PESs), on the sub-reactive or reactive collision dynamics during the past decade. [15][16][17][18][19][20][21][22][23][24][25][26][27][28] The ground state potential energy surface (PES) of LiH 2 system for the collinear arrangement was initially constructed by Clarke et al 16 and also for the threedimensional configurations by Dunne, Murrell, and Jemmer (DMJ PES). 18 Clarke and coworkers 16 have calculated the initial state selected reaction probabilities for the depletion and formation reaction of LiH by the quasi-classical trajectory (QCT) and the quantum time-dependent wave packet method for the special collinear arrangement.…”

Potential Energy Surfaces for the Reaction Al + O2→ AlO + O

“…Thus the reaction mechanism appears similar to the hydrogenation reaction of the alkali atom studied by our group. 15,16 In summary, the end-on geometry is the most favourable for the reaction to take place. It is at the same time closer to the reactant and the product than the C 2v intermediate isomer.…”