A simple C++ code to run path integral molecular dynamics (PIMD) for water clusters. Several trajectories can be ran in parallel at different temperatures taking advantage of the replica-exchange method. PIMD propagator is from the following papers:

J. Chem. Phys. 99, 2796 (1993); DOI: 10.1063/1.465188 "Efficient molecular dynamics and hybrid Monte Carlo algorithms for path integrals" Mark E. Tuckerman, Bruce J. Berne, Glenn J. Martyna, and Michael L. Klein

J. Chem. Phys. 110, 3275 (1999); DOI: 10.1063/1.478193 "Molecular dynamics algorithms for path integrals at constant pressure" Glenn J. Martyna, Adam Hughes, and Mark E. Tuckerman