I've come across many papers performing ab initio MD (Carr-Parinello or Born-Oppenheimmer) simulations of water that use the deuterium mass for hydrogen. And they state that this helps improve convergence. I haven't seen a derivation for it and I'm not able to come up with an intuitive reason for why this might be. I would greatly appreciate some insights.
Here's an example of a paper that does so (I'm linking this because it doesn't seem to need institutional credentials to access): https://www.spiedigitallibrary.org/journals/Journal-of-Photonics-for-Energy/volume-1/issue-1/016002/iAb-initio-i-modeling-of-water-semiconductor-interfaces-for-photocatalytic/10.1117/1.3625563.full?SSO=1