FHI-aims

Introduction

FHI-aims is a all-electron full-potential density functional theory code using a numeric local orbital basis set.

Running the Calculator

The default initialization command for the FHI-aims calculator is

class ase.calculators.aims.Aims(profile=None, directory='.', **kwargs)[source]

Construct the FHI-aims calculator.

The keyword arguments (kwargs) can be one of the ASE standard keywords: ‘xc’, ‘kpts’ and ‘smearing’ or any of FHI-aims’ native keywords.

Arguments:

cubes: AimsCube object: Cube file specification.
tier: int or array of ints: Set basis set tier for all atomic species.
plus_udict: For DFT+U. Adds a +U term to one specific shell of the species.
kwargsdict: Any of the base class arguments.

In order to run a calculation, you have to ensure that at least the following str variables are specified, either in the initialization or as shell environment variables:

keyword	description
`run_command`	The full command required to run FHI-aims from a shell, including anything to do with an MPI wrapper script and the number of tasks, e.g.: `mpiexec aims.081213.scalapack.mpi.x > aims.out`. An alternative way to set this command is via the `ASE_AIMS_COMMAND` environment variable.
`species_dir`	Directory where the species are located, e.g.: `/opt/fhi-aims-081213/species_defaults/light`. Can also be specified with the `AIMS_SPECIES_DIR` environment variable.
`xc`	which exchange-correlation functional is used.

List of keywords

This is a non-exclusive list of keywords for the control.in file that can be addresses from within ASE. The meaning for these keywords is exactly the same as in FHI-aims, please refer to its manual for help on their use.

One thing that should be mentioned is that keywords with more than one option have been implemented as tuples/lists, eg. k_grid=(12,12,12) or relativistic=('atomic_zora','scalar'). In those cases, specifying a single string containing all the options is also possible.

None of the keywords have any default within ASE, but do check the defaults set by FHI-aims.

Example keywords describing the computational method used:

keyword	type
`xc`	str
`charge`	float
`spin`	str
`relativistic`	list
`use_dipole_correction`	bool
`vdw_correction_hirshfeld`	str
`k_grid`	list

Note

Any argument can be changed after the initial construction of the calculator, simply by setting it with the method

>>> calc.set(keyword=value)

Volumetric Data Output

The class

class ase.calculators.aims.AimsCube(origin=(0, 0, 0), edges=[(0.1, 0.0, 0.0), (0.0, 0.1, 0.0), (0.0, 0.0, 0.1)], points=(50, 50, 50), plots=())[source]

Object to ensure the output of cube files, can be attached to Aims object

parameters:

origin, edges, points:: Same as in the FHI-aims output
plots:: what to print, same names as in FHI-aims

describes an object that takes care of the volumetric output requests within FHI-aims. An object of this type can be attached to the main Aims() object as an option.

The possible arguments for AimsCube are:

keyword	type
`origin`	list
`edges`	3x3-array
`points`	list
`plots`	list

The possible values for the entry of plots are discussed in detail in the FHI-aims manual, see below for an example.

Example

Here is an example of how to obtain the geometry of a water molecule, assuming ASE_AIMS_COMMAND and AIMS_SPECIES_DIR are set: :git:`ase/test/calculator/aims/test_H2O_aims.py`.

import pytest

from ase import Atoms
from ase.calculators.aims import AimsCube
from ase.optimize import QuasiNewton


@pytest.mark.calculator('aims')
def test_H2O_aims(factory):
    water = Atoms('HOH', [(1, 0, 0), (0, 0, 0), (0, 1, 0)])

    water_cube = AimsCube(points=(29, 29, 29),
                          plots=('total_density',
                                 'delta_density',
                                 'eigenstate 5',
                                 'eigenstate 6'))

    calc = factory.calc(
        xc='LDA',
        output=['dipole'],
        sc_accuracy_etot=1e-2,
        sc_accuracy_eev=1e-1,
        sc_accuracy_rho=1e-2,
        sc_accuracy_forces=1e-1,
        cubes=water_cube
    )

    water.calc = calc
    dynamics = QuasiNewton(water)
    dynamics.run(fmax=0.2)