In many chemical reactions, the wavefunction of the entire system can be expressed as a single adiabatic potential energy surface (instead of a linear combination of several adiabatic surfaces). Often, this adiabatic PES corresponds to the ground-state of the species involved in the chemical reaction. For example, when we draw a reaction path depicting the transformation of the reactants (HCl + C 2 H 5 Br) into the products (HBr + C 2 H 5 Cl) through a transition state (C 2 H 5 BrCl), we inherently assume that these reactions occur along the ground-state PES (through a specific reaction coordinate). These chemical processes, where the wavefunction is confined to a single PES, are termed as adiabatic processes (see left panel of Fig. ) and can be accurately described by the TISE (i.e., when the nuclear dynamics are governed by a single adiabatic PES, it is within the realm of the adiabatic dynamics). Born-Oppenheimer molecular dynamics and Car-Parrinello molecular dynamics are examples of such ab-initio adiabatic dynamics, and many electronic structure packages such as CP2K, Quantum Espresso, VASP, SIESTA, NWChem, and DFTB+ 57 are routinely used by many researchers to calculate on-the-fly adiabatic dynamics.