On the evaluation of nonadiabatic coupling matrix elements using SA-MCSCF/CI wave functions and analytic gradient methods. I

A method for the efficient evaluation of nonadiabatic coupling matrix elements of the form 〈ΨI‖∂/∂RαΨJ〉 is presented. The wave functions ΨI and ΨJ are assumed to be multiconfiguration self-consistent field (MCSCF) wave functions optimized within the state averaged approximation. The method, which ca...

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Bibliographic Details
Published in:The Journal of chemical physics 1984-11, Vol.81 (10), p.4549-4553
Main Authors: LENGSFIELD, B. H. III, SAXE, P, YARKONY, D. R
Format: Article
Language:English
Subjects:
Atomic and molecular collision processes and interactions
Atomic and molecular physics
Exact sciences and technology
Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
Physics
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Summary:A method for the efficient evaluation of nonadiabatic coupling matrix elements of the form 〈ΨI‖∂/∂RαΨJ〉 is presented. The wave functions ΨI and ΨJ are assumed to be multiconfiguration self-consistent field (MCSCF) wave functions optimized within the state averaged approximation. The method, which can treat several states simultaneously, derives its efficiency from the direct solution of the coupled perturbed state averaged MCSCF equations and the availability of other appropriate derivative integrals. An extension of this approach to SA-MCSCF/CI wave functions is described. Here it is shown that computational efficiencies can be achieved by exploiting analogies with analytic CI gradient methods. Numerical examples for C2v approach of Mg to H2 are presented.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.447428