  We present an improved method for determining guess structures for transition
state searches by incorporating internal coordinates interpolation into the
freezing string method (FSM). We test our method on over 40 reactions across 3
benchmark datasets covering a diverse set of chemical reactions. Our results
show that incorporation of internal coordinates interpolation improves the
computational efficiency of the FSM by enabling the use of larger interpolation
step sizes and fewer optimization steps per cycle while maintaining 100%
success rate on benchmark chemical reaction test cases including systems where
previous attempts based on linear synchronous transit interpolation have
failed. We provide an open-source Python implementation of the FSM, in addition
to the reactant, product, transition state structures of all reactions studied.
