On the evaluation of nonadiabatic coupling matrix elements for MCSCF/CI wave functions. IV. Second derivative terms using analytic gradient methods

Journal Article · Thu Jan 01 00:00:00 EST 1987 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.452621· OSTI ID:6838771

Saxe, P; Yarkony, D R

A recently proposed methodology for determining second derivative nonadiabatic coupling matrix elements h(J,I,R/sub ..cap alpha../,R) equivalent/sub r/ based on analytic gradient methods is implemented and discussed. Here r denotes the electronic coordinates, R the nuclear coordinates, and the Psi/sub J/ (r;R) are eigenfunctions of the nonrelativistic Born--Oppenheimer Hamiltonian at the state averaged MCSCF/CI level. The region of a conical intersection of the 1,2 /sup 2/A' potential energy surfaces of the Li--H/sub 2/ system is considered in order to illustrate the potential of this approach. The relation between h(J,I,R/sub ..cap alpha../,R) and the first derivative matrix elements g(J,I,R/sub ..cap alpha../,R) equivalent/sub r/ is considered and the role of symmetry discussed. The h(J,I,R/sub ..cap alpha../,R) are analyzed in terms of contributions from molecular orbital and CI coefficient derivatives and the importance of the various nuclear degree of freedom, R/sub ..cap alpha../, is considered. It is concluded that for the case considered a flexible multiconfiguration wave function is desirable for characterizing h(J,I,R/sub ..cap alpha../,R).

• Research Organization: Los Alamos National Laboratory, Los Alamos, New Mexico 87545
• OSTI ID: 6838771
• Journal Information: J. Chem. Phys.; (United States), Vol. 86:1
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ELECTRONIC STRUCTURE
CONFIGURATION INTERACTION
HYDROGEN
LITHIUM
INTERATOMIC FORCES
MATRIX ELEMENTS
POTENTIAL ENERGY
WAVE FUNCTIONS
ALKALI METALS
ELEMENTS
ENERGY
FUNCTIONS
METALS
NONMETALS
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory