Algorithmic description of implementing path integral molecular dynamics?

Question

Suppose I have a functioning molecular dynamics package for classical MD. I want to extend this code to run path integral MD. I know that a surprisingly small number of new features need to be implemented, but the literature I am aware of is quite formal, where I'd be interested to look at a more algorithmic description of what steps need to be added to the usual integration of Newton's equations in classical MD.

Any references, books or articles, you've seen which fit the description, I'd love to look at. Alternatively, a simple reference implementation would be nice. It's quite easy to find reference implementations of path integral monte carlo, but not as much PIMD.

Answer 1

Just as in normal MD, there are different integration schemes for PIMD. Here's one that I think has a pretty clear description from an algorithmic perspective: https://doi.org/10.1063/1.3489925

The PILE-L algorithm described in that has been implemented in OpenMM. Most of the implementation is in ReferenceRpmdKernels.cpp, but other parts of the plugin may also be useful. And, of course, since this is part of a large package, it isn't the simplest implementation possible.