  Coupled trajectory mixed quantum classical (CTMQC) dynamics is a rigorous
approach to trajectory-based non-adiabatic dynamics, which has recently seen an
improvement to energy conservation via the introduction of the CTMQC-E
algorithm. Despite this, the method's two key quantities distinguishing it from
Ehrenfest dynamics, the modified Born-Oppenheimer momentum and the quantum
momentum, require regularisation procedures in certain circumstances. Such
procedures in the latter can cause instabilities leading to undesirable effects
such as energy drift and spurious population transfer, which is expected to
become increasingly prevalent the larger the system as such events would happen
more frequently. We propose a further modification to CTMQC-E which includes a
redefinition of the quantum momentum, CTMQC-EDI (Double Intercept), such that
it has no formal divergences. We then show for Tully models I-IV that the
algorithm has greatly improved total energy conservation and negligible
spurious population transfer at all times, in particular in regions of strong
non-adiabatic coupling. CTMQC-EDI therefore shows promise as a numerically
robust non-adiabatic dynamics technique that accounts for decoherence from
first principles and that is scalable to large molecular systems and materials.
