The OpenMM code was referred/adapted from the following resources:

1. The AMD integrators in OpenMM written by Peter Eastman
2. The OpenMM code for GaMD from LJMatrin: https://github.com/ljmartin/openmm_gamd/tree/master
3. The code from Alex Izvoski posted at openmm/openmm#3281

Pengfei Li acknowledge the efforts of these folks.

OpenMM 8.0.0 and ParmEd 3.4.3 were used for the simulations, while a different version (combination) may not work.