Thank you for contacting us and let me answer your question as follows.
(1) In AIMD (Ab Initio Molecular Dynamics) simulations, the most time-consuming part is the self-consistent DFT calculation of the forces between atoms, especially when the system involves a large number of atoms. The RESCU+ package provides the DFT method of calculating forces for large systems.
(2) After the forces are obtained on each atom by RESCU+, molecular dynamics (MD) moves the atoms according to the Newton's 2nd law with additional physics regarding thermodynamics. After new positions of the atoms are obtained, we do (1) again to compute the forces in the next step by RESCU+, and the process is repeated until done. Together, the RESCU+ plus a MD integrator, is called "Born-Oppenheimer AIMD", which is the AIMD provided to you.
(3) The MD integrator (solving Newton's equation with a thermostat) is via ASE, at this moment. Since the MD algorithm accounts for a very tiny portion of the entire AIMD simulation burden, we have not created a separate MD integrator inside RESCU+. That's why you need to use ASE in combination with RESCU+, and the combination is the AIMD which we provided.
Thanks for your question and please do not hesitate to contact me if further questions arise.
