i-PI path integral MD with AMS

Note: This example requires AMS2023 or later.

This example shows how to couple the i-PI code to AMS using the AMS ASE calculator.

i-PI can be used to run for example path integral molecular dynamics. The example shows how to run thermostatted ring polymer molecular dynamics for a water molecule together with the UFF force field.

For more information about i-PI, refer to the i-PI documentation and examples.

The below example only runs on Linux as it uses a unix socket.

Technical

i-PI is not included with AMS and is not supported by SCM.

Example usage: (Download run-ase.py and auxiliary files input.xml, firstframe.xyz, run-server.sh)

#!/usr/bin/env amspython
from ase.calculators.socketio import SocketClient
from ase.io import read
from scm.plams import Settings
from scm.plams.interfaces.adfsuite.ase_calculator import AMSCalculator

"""
Example illustrating how to use AMS as a client together with i-PI.

The i-PI configuration in input.xml sets up a short ring-polymer molecular
dynamics (RPMD) simulation. 

The connection between server and client is of type 'unixsocket' (a file in
/tmp). This example will only run on Linux.

The settings below set up AMS to use the UFF force field to calculate the
energy, forces, and stress tensor of whatever system the i-PI server requests
and return them to i-PI.

AMS is run in "AMSWorker" mode (interactive mode), which means that AMS does
**not** shut down and start up again between calculations.

To run this example, 

* modify run-server.sh to provide the correct path to the i-pi executable,
* sh run-server.sh
* In a different terminal: $AMSBIN/amspython run-ase.py
"""


def main():

    use_stress = False
    atoms = read("firstframe.xyz")

    sett = Settings()
    sett.input.ams.Task = "SinglePoint"
    sett.input.ams.Properties.Gradients = "True"
    sett.input.ams.Properties.StressTensor = str(use_stress)
    sett.input.forcefield.type = "UFF"
    sett.runscript.nproc = 1

    with AMSCalculator(settings=sett, amsworker=True) as calc:
        atoms.calc = calc
        client = SocketClient(unixsocket="driver-irpmd-16")  # socket should match the one given in input.xml
        client.run(atoms, use_stress=use_stress)


if __name__ == "__main__":
    main()