期刊
JOURNAL OF CHEMICAL PHYSICS
卷 120, 期 16, 页码 7330-7339出版社
AMER INST PHYSICS
DOI: 10.1063/1.1668631
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The method for the analytic calculation of the nonadiabatic coupling vector at the multireference configuration-interaction (MR-CI) level and its program implementation into the COLUMBUS program system described in the preceding paper [Lischka , J. Chem. Phys. 120, 7322 (2004)] has been combined with automatic searches for minima on the crossing seam (MXS). Based on a perturbative description of the vicinity of a conical intersection, a Lagrange formalism for the determination of MXS has been derived. Geometry optimization by direct inversion in the iterative subspace extrapolation is used to improve the convergence properties of the corresponding Newton-Raphson procedure. Three examples have been investigated: the crossing between the 1 B-1(1)/2 (1)A(1) valence states in formaldehyde, the crossing between the 2 (1)A(1)/3 (1)A(1) pi-pi(*) valence and n(y)-3p(y) Rydberg states in formaldehyde, and three crossings in the case of the photodimerization of ethylene. The methods developed allow MXS searches of significantly larger systems at the MR-CI level than have been possible before and significantly more accurate calculations as compared to previous complete-active space self-consistent field approaches. (C) 2004 American Institute of Physics.
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