jz6b02501_si_001.pdf (165.85 kB)
Estimating the Derivative Coupling Vector Using Gradients
journal contribution
posted on 2016-11-23, 00:00 authored by Joshua
A. Kammeraad, Paul M. ZimmermanThe
difference gradient and derivative coupling vectors span the
branching planes of conical intersections between electronic states.
While gradients are commonly available in many electronic structure
methods, the derivative coupling vectors are not always implemented
and ready for use in characterizing conical intersections. This Letter
shows how the derivative coupling vectors can be computed to high
accuracy (direction and magnitude) using energy and gradient information.
The new method is based on the combination of a linear-coupling two-state
Hamiltonian and a finite-difference Davidson approach for computing
the branching plane. Benchmark cases are provided showing these vectors
can be efficiently computed near conical intersections.