Getting Started

Installation

SEAMM MDI is a Python library. It depends on the pymdi package (the MDI Library’s Python bindings), numpy, and seamm-util (for unit handling).

pip install seamm_mdi

To actually run a calculation you also need an engine — an external code wrapped as an MDI engine — installed and reachable. SEAMM ships small engine wrappers for MOPAC and xTB (in the mopac_step / xtb_step packages); the engine runs the code through its Python API and speaks the MDI protocol, so it needs only the code and pymdi, not SEAMM itself.

A first engine

MDIEngine is the driver. You give it a callable that builds the command to launch the engine (pointed at the driver’s hostname/port) and the list of atomic numbers, then drive it:

import numpy as np
from seamm_mdi import MDIEngine

def build_argv(hostname, port):
    # Whatever launches your MDI engine wrapper, pointed at the driver.
    return [
        "python", "my_engine.py", "-mdi",
        f"-role ENGINE -name MYCODE -method TCP -port {port} "
        f"-hostname {hostname}",
    ]

# A water molecule (O, H, H).
xyz = np.array([[0.0, 0.0, 0.0], [0.76, 0.59, 0.0], [-0.76, 0.59, 0.0]])

with MDIEngine(build_argv, elements=[8, 1, 1]) as engine:
    engine.set_coordinates(xyz, units="Å")
    print("energy:", engine.energy(units="kcal/mol"), "kcal/mol")

The engine is launched once when the with block is entered and shut down cleanly when it exits; in between you can call set_coordinates / energy / forces as many times as you like.

In practice a SEAMM step builds build_argv from a model chemistry (get_mdi_engine_command on the owning program step), so the user just “sets up a model chemistry and goes”. See the User Guide.