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   "source": [
    "## i-PI path integral MD with AMS\n",
    "\n",
    "This example prepares the files needed to couple [i-PI](https://ipi-code.org/) to AMS through the ASE socket interface.\n",
    "\n",
    "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.\n",
    "\n",
    "For more information about i-PI, refer to the i-PI documentation and examples.\n",
    "\n",
    "Note that the provided setup uses a Unix socket and therefore runs on Linux."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "04e4ca67-7c38-49e9-9673-fe8676a2f878",
   "metadata": {},
   "source": [
    "### Create Input File for i-PI"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5a215d57-28f0-4266-9838-060cff56d314",
   "metadata": {},
   "source": [
    "First, write the input for i-PI to an xml file."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "a6a75f30-378a-40c4-9802-69b92713ba2a",
   "metadata": {},
   "outputs": [],
   "source": [
    "from pathlib import Path\n",
    "\n",
    "Path(\"input.xml\").write_text(\n",
    "    \"\"\"\\\n",
    "<simulation mode=\"md\" verbosity=\"medium\">\n",
    "   <output prefix='simulation'>\n",
    "      <properties stride='10' filename='out'> [ step, time{picosecond}, conserved{electronvolt}, temperature{kelvin}, pressure_cv{megapascal} ] </properties>\n",
    "      <trajectory filename='pos' stride='10'> positions{angstrom} </trajectory>\n",
    "      <trajectory filename='xc' stride='10'> x_centroid{angstrom} </trajectory>\n",
    "      <trajectory filename='vc' stride='10'> v_centroid </trajectory>\n",
    "      <checkpoint stride='4000'/>\n",
    "   </output>\n",
    "   <total_steps> 40 </total_steps>\n",
    "   <!-- <total_time> 840000000 </total_time> -->\n",
    "   <prng><seed> 31415 </seed></prng>\n",
    "   <ffsocket name=\"ase\" mode=\"unix\">\n",
    "      <address> driver-irpmd-16 </address>\n",
    "   </ffsocket>\n",
    "   <system>\n",
    "      <initialize nbeads='8'>\n",
    "         <file mode='xyz' units='angstrom'> firstframe.xyz </file>\n",
    "         <velocities mode=\"thermal\" units='kelvin'> 300 </velocities>\n",
    "         <cell units='angstrom' mode='abc'> [ 12.412, 12.412, 12.412 ] </cell>\n",
    "      </initialize>\n",
    "      <forces><force forcefield=\"ase\"> </force></forces>\n",
    "      <motion mode='dynamics'>\n",
    "         <dynamics mode='nvt'>\n",
    "           <timestep units='femtosecond'> 0.25 </timestep>\n",
    "           <thermostat mode='pile_g'>\n",
    "             <tau units='femtosecond'> 100 </tau>\n",
    "             <pile_lambda> 0.5 </pile_lambda>\n",
    "           </thermostat> \n",
    "         </dynamics>\n",
    "      </motion>\n",
    "      <ensemble>\n",
    "         <temperature units='kelvin'> 300 </temperature>\n",
    "      </ensemble>\n",
    "   </system>\n",
    "</simulation>\n",
    "    \"\"\"\n",
    ");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "b3959215-fe9e-45b6-8b7d-f1a75a664ab4",
   "metadata": {},
   "source": [
    "Create a simple xyz file with a water molecule:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "1b40644a-85c3-4a02-a0d4-3195579800ea",
   "metadata": {},
   "outputs": [],
   "source": [
    "Path(\"firstframe.xyz\").write_text(\n",
    "    \"\"\"\\\n",
    "3\n",
    "\n",
    "O -0.691870 1.324715 0.212227\n",
    "H -1.523797 1.656370 -0.135379\n",
    "H -0.797941 0.389809 0.486593\n",
    "VEC1 12.412 0. 0.\n",
    "VEC2 0. 12.412 0.\n",
    "VEC3 0. 0. 12.412\n",
    "\"\"\"\n",
    ");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "87186350-328c-4539-8f4c-89f21071b637",
   "metadata": {},
   "source": [
    "Create script to launch i-PI server (the variable `ipi_exec` can be adjusted to your installation)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "64b7e733-0796-4cdc-8274-1cabfe522eac",
   "metadata": {},
   "outputs": [],
   "source": [
    "ipi_exec = \"i-pi\"\n",
    "Path(\"run-server.sh\").write_text(\n",
    "    f\"\"\"\\\n",
    "#!/usr/bin/env bash\n",
    "# Example launcher for i-PI server \n",
    "{ipi_exec} input.xml\n",
    "\"\"\"\n",
    ");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "af35bb75-1e22-43f6-b29d-304dd571c461",
   "metadata": {},
   "source": [
    "### Launch the i-PI Server"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c5dac2a1-70e6-442b-b560-42fbde579ee1",
   "metadata": {},
   "source": [
    "Now in a separate window, run `sh run-server.sh`. Once the server is up and running we can proceed with the AMS calculation. \n",
    "\n",
    "i-PI is external to AMS and must be installed separately. The provided setup uses a Unix socket and therefore runs on Linux and Mac."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "ec6a53eb-e98e-41de-bda3-ee061dde6219",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Start i-PI server by running in a new terminal: 'sh run-server.sh'\n"
     ]
    }
   ],
   "source": [
    "print(\"Start i-PI server by running in a new terminal: 'sh run-server.sh'\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5b8b8ef2-50be-4d90-82df-918f8da997f6",
   "metadata": {},
   "source": [
    "### Run AMS Calculator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "e6099562-47c0-4e4d-b288-9d05d64454a9",
   "metadata": {},
   "outputs": [],
   "source": [
    "from ase.calculators.socketio import SocketClient\n",
    "from ase.io import read\n",
    "from scm.plams import Settings, from_smiles\n",
    "from scm.plams.interfaces.adfsuite.ase_calculator import AMSCalculator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "3a129580-fd1b-4a7f-94c3-4800d655154b",
   "metadata": {},
   "outputs": [],
   "source": [
    "atoms = read(\"firstframe.xyz\")\n",
    "\n",
    "sett = Settings()\n",
    "sett.input.ams.Task = \"SinglePoint\"\n",
    "sett.input.ams.Properties.Gradients = \"True\"\n",
    "sett.input.ams.Properties.StressTensor = \"False\"\n",
    "sett.input.forcefield.type = \"UFF\"\n",
    "sett.runscript.nproc = 1\n",
    "\n",
    "with AMSCalculator(settings=sett, amsworker=True) as calc:\n",
    "    atoms.calc = calc\n",
    "    client = SocketClient(unixsocket=\"driver-irpmd-16\")\n",
    "    client.run(atoms, use_stress=False)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "4a4fcc93-d51b-4949-8a3b-18f1bb7cda56",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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