Interactions of Excited Lithium Atom with Molecular Hydrogen. III. Orthogonality Constrained MCSCF+NCI Calculations of Potential Energy Surfaces and Electronic Wave Functions in the Potential Crossing Region

Abstract

A method of calculating the excited state MCSCF electronic wave function by constraining it to be orthogonal to the predetermined ground state wave function was applied to calculate wave functions of the Li–H2 system near the center of a conical intersection of the lowest two potential energy surfaces. Combined with an additional nonorthogonal configuration interaction process, it has proved to be an efficient method to get systems of wave functions that are continuous throughout whole geometries. Qualitative characters of wave functions near the center of potential crossing previously inferred have been reconfirmed.

Quenching of Li ( 2 P) by H 2 : potential energy surfaces, conical intersection seam, and diabatic bases

“…The MECP on the [11], and Saxe and Yarkony [70], R mex 3X0Y 1X9Y 90 , and is in satisfactory accord with the more recent result of Martinez [20], R mex 2X86 AE 0X01Y 1X78 AE 0X01Y 90 . Table 1 reports and Fig.…”

Structure and Stability of M−H2 Complexes

“…5 Potential energy surfaces of Li-H 2 ground and lowest excited electronic states, including crossing regions, have been studied with MCSCF wave functions and rather small basis states (4-31G*). [6][7] A minimum with D e about 10 kcal/mol was found on the 2 B 2 surface, and the transition from 2 B 2 to 2 A 1 was predicted to occur with high probability. Potential energy surfaces have also been studied for Na-H 2 , [8][9][10] Be-H 2 , [11][12][13] and Mg-H 2 [13][14][15] excited states.…”

“…The Li-H 2 system has been of particular interest because of the low mass of Li. Both the ground and excited states have been studied previously. − Hobza and Schleyer 3 studied Li−H 2 at the MP2/6-311G (2d,2p) level of theory and found a weakly bound complex (∼7 cm -1 binding energy) for the ground state linear configuration and a much stronger complex (16.4 kcal/mol) for the excited state ( 2 B 2 ). Konowalow found the linear van der Waals complex to have a dissociation energy ( D e ) between 13 and 18 cm -1 using the interacting correlated fragments (ICF) method and large basis sets…”

“…Konowalow found the linear van der Waals complex to have a dissociation energy ( D e ) between 13 and 18 cm -1 using the interacting correlated fragments (ICF) method and large basis sets − A minimum with D e about 10 kcal/mol was found on the 2 B 2 surface, and the transition from 2 B 2 to 2 A 1 was predicted to occur with high probability. Potential energy surfaces have also been studied for Na−H 2 , − Be−H 2 , − and Mg−H 2 − excited states.…”

Interfacing Electronic Structure Theory with Dynamics

“…D. AlH 2 . There has been considerable recent interest in the possible existence of weakly interacting complexes between the lighter metals M in the second and third periods and clusters of molecular hydrogen. − Here, we focus on M = Al.…”