CHAMP Calculator

Setting up the calculator

The CHAMP calculator can used in ASE for any kind of simulation. After importing the calculator, a new CHAMP calculator object can be made using:

>>> from qmcblip.champ import CHAMP
>>> champ_calc = CHAMP(champ_loc="/home/user/champ/bin/vmc.mov1", force_file="write_forces", ncore=4)

To view all the parameters that can be passed to the calculator, see the CHAMP class documentation.

To attach this calculator to a molecule and do Molecular Dynamics, we can do:

>>> from ase.md.verlet import VelocityVerlet
>>> from ase.build import molecule
>>>
>>> # Make a H2 molecule
>>> atoms = molecule("H2")
>>>
>>> # Attach the calculator
>>> atoms.calc = champ_calc
>>>
>>> # Setup and run MD
>>> dyn = VelocityVerlet(atoms, 0.5 * units.fs)
>>> dyn.run(30)

Configuring CHAMP

There are two methods of configuring CHAMP. You can have a vmc.inp file in the same directory as the Python script. This vmc.inp file should contain all the neccessery settings. The second method is by passing a Settings object to the CHAMP calculator, using the settings keyword argument. A Settings object can be created by reading from a vmc.inp file (see qmcblip.champio.Settings.read()):

>>> from qmcblip.champio import Settings
>>> settings = Settings.read('vmc.inp')
>>>
>>> champ_calc = CHAMP(settings=settings)

It can also be created by creating it explicitly in Python and passing the neccessery arguments:

>>> settings = Settings(...)

See the Settings documentation for an overview of which parameters are required. Once you have a Settings object, it can also be printed to a vmc.inp file (see qmcblip.champio.Settings.write()):

>>> settings.write('vmc.inp')