The Pymatgen python library allows to setup
solid-state calculations using a flexible set of classes as well as an API
to an online data base of structures. Its Structure and Lattice
objects are directly supported by the DFTK load_atoms and load_lattice
functions, such that DFTK may be readily used to run calculation on systems
defined in pymatgen. Using the pymatgen_structure function a conversion
from DFTK to pymatgen structures is also possible. In the following we
use this to create a silicon supercell and find its LDA ground state
using direct minimisation.
First we setup the silicon lattice in DFTK.
using DFTK
a = 10.263141334305942 # Lattice constant in Bohr
lattice = a / 2 .* [[0 1 1.]; [1 0 1.]; [1 1 0.]]
Si = ElementPsp(:Si, psp=load_psp("hgh/lda/Si-q4"))
atoms = [Si => [ones(3)/8, -ones(3)/8]];
Next we make a [2, 2, 2] supercell using pymatgen
pystruct = pymatgen_structure(lattice, atoms)
pystruct.make_supercell([2, 2, 2])
lattice = load_lattice(pystruct)
atoms = [Si => [s.frac_coords for s in pystruct.sites]];
Setup an LDA model and discretize using
a single kpoint and a small Ecut of 5 Hartree.
model = model_LDA(lattice, atoms)
basis = PlaneWaveBasis(model, 5, kgrid=(1, 1, 1))
Find the ground state using direct minimisation (always using SCF is boring ...)
scfres = direct_minimization(basis, tol=1e-5);
scfres.energies