Gradients and Non-Adiabatic Derivative Coupling Terms for Spin-Orbit Wavefunctions

Analytic gradients of electronic eigenvalues require one calculation per nuclear geometry, compared to 3n calculations for finite difference methods, where n is the number of nuclei. Analytic non-adiabatic derivative coupling terms, which are calculated in a similar fashion, are used to remove non-diagonal contributions to the kinetic energy operator, leading to more accurate nuclear dynamics calculations than those that employ the Born-Oppenheimer approximation and assume off-diagonal contributions are zero. The current methods and underpinnings for calculating both of these quantities for MRCI-SD wavefunctions in COLUMBUS are reviewed. Before this work, these methods were not available for wavefunctions of a relativistic MRCI-SD Hamiltonian. A formalism for calculating the density matrices, analytic gradients, and analytic derivative coupling terms for those wavefunctions is presented. The results of a sample calculation using a Stuttgart basis for K He are presented.

Author: Lachlan T. Belcher
Publisher: Biblioscholar
Published: 11/19/2012
Pages: 230
Binding Type: Paperback
Weight: 0.92lbs
Size: 9.69h x 7.44w x 0.48d
ISBN: 9781288315710

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