Atomistic simulations of nonadiabatic photodynamics require derivative coupling vectors—or some approximate substitute—to meaningfully describe transitions between electronic states. These vectors are usually only available for specific electronic structure methods such as CASSCF and TD-DFT, limiting the applicability of other theories for use in dynamics simulations. In this talk, we describe an approach for constructing accurate derivative coupling vectors from energies and gradients of the two interacting states. To do so, we construct a representation of the branching plane using submatrix diagonalization at low cost and without specific reference to the underlying quantum chemical theory. Overall, this procedure is therefore widely applicable to many levels of electronic structure theory. Benchmarks comparing the approximate derivative coupling vector directions and magnitudes to exact derivative coupling vectors from CASSCF will demonstrate the high accuracy obtainable using this method.

Derivative coupling vectors from a Davidson approach

253rd National Meeting (2017)

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