AtomsBase integration
AtomsBase.jl is a common interface for representing atomic structures in Julia. DFTK directly supports using such structures to run a calculation as is demonstrated here.
using DFTK
using AtomsBuilderFeeding an AtomsBase AbstractSystem to DFTK
In this example we construct a bulk silicon system using the bulk function from AtomsBuilder. This function uses tabulated data to set up a reasonable starting geometry and lattice for bulk silicon.
system = bulk(:Si)FlexibleSystem(Si₂, periodicity = TTT):
cell_vectors : [ 0 2.715 2.715;
2.715 0 2.715;
2.715 2.715 0]u"Å"
Atom(Si, [ 0, 0, 0]u"Å")
Atom(Si, [ 1.3575, 1.3575, 1.3575]u"Å")
By default the atoms of an AbstractSystem employ the bare Coulomb potential. To employ pseudpotential models (which is almost always advisable for plane-wave DFT) one employs the pseudopotential keyword argument in model constructors such as model_DFT. For example we can employ a PseudoFamily object from the PseudoPotentialData package. See its documentation for more information on the available pseudopotential families and how to select them.
using PseudoPotentialData # defines PseudoFamily
pd_lda_family = PseudoFamily("dojo.nc.sr.lda.v0_4_1.standard.upf")
model = model_DFT(system; functionals=LDA(), temperature=1e-3,
pseudopotentials=pd_lda_family)Model(lda_x+lda_c_pw, 3D):
lattice (in Bohr) : [0 , 5.13061 , 5.13061 ]
[5.13061 , 0 , 5.13061 ]
[5.13061 , 5.13061 , 0 ]
unit cell volume : 270.11 Bohr³
atoms : Si₂
pseudopot. family : PseudoFamily("dojo.nc.sr.lda.v0_4_1.standard.upf")
num. electrons : 8
spin polarization : none
temperature : 0.001 Ha
smearing : DFTK.Smearing.FermiDirac()
terms : Kinetic()
AtomicLocal()
AtomicNonlocal()
Ewald(nothing)
PspCorrection()
Hartree()
Xc(lda_x, lda_c_pw)
Entropy()Alternatively the pseudopotentials object also accepts a Dict{Symbol,String}, which provides for each element symbol the filename or identifier of the pseudopotential to be employed, e.g.
path_to_pspfile = PseudoFamily("cp2k.nc.sr.lda.v0_1.semicore.gth")[:Si]
model = model_DFT(system; functionals=LDA(), temperature=1e-3,
pseudopotentials=Dict(:Si => path_to_pspfile))Model(lda_x+lda_c_pw, 3D):
lattice (in Bohr) : [0 , 5.13061 , 5.13061 ]
[5.13061 , 0 , 5.13061 ]
[5.13061 , 5.13061 , 0 ]
unit cell volume : 270.11 Bohr³
atoms : Si₂
atom potentials : ElementPsp(:Si, "/home/runner/.julia/artifacts/966fd9cdcd7dbaba6dc2bf43ee50dd81e63e8837/Si.gth")
ElementPsp(:Si, "/home/runner/.julia/artifacts/966fd9cdcd7dbaba6dc2bf43ee50dd81e63e8837/Si.gth")
num. electrons : 8
spin polarization : none
temperature : 0.001 Ha
smearing : DFTK.Smearing.FermiDirac()
terms : Kinetic()
AtomicLocal()
AtomicNonlocal()
Ewald(nothing)
PspCorrection()
Hartree()
Xc(lda_x, lda_c_pw)
Entropy()We can then discretise such a model and solve:
basis = PlaneWaveBasis(model; Ecut=15, kgrid=[4, 4, 4])
scfres = self_consistent_field(basis, tol=1e-8);n Energy log10(ΔE) log10(Δρ) Diag Δtime
--- --------------- --------- --------- ---- ------
1 -7.921704263420 -0.69 5.4 188ms
2 -7.926138355446 -2.35 -1.22 1.0 251ms
3 -7.926833842237 -3.16 -2.37 2.0 160ms
4 -7.926861311180 -4.56 -3.03 3.2 238ms
5 -7.926861657220 -6.46 -3.49 1.9 162ms
6 -7.926861676780 -7.71 -4.10 2.0 161ms
7 -7.926861676565 + -9.67 -4.01 1.8 164ms
8 -7.926861681148 -8.34 -4.35 1.0 141ms
9 -7.926861681825 -9.17 -4.73 1.4 154ms
10 -7.926861681858 -10.47 -5.25 1.2 148ms
11 -7.926861681870 -10.92 -5.60 1.2 152ms
12 -7.926861681872 -11.65 -6.70 1.8 163ms
13 -7.926861681873 -12.95 -6.63 2.8 189ms
14 -7.926861681873 + -14.75 -6.75 1.0 175ms
15 -7.926861681873 -14.10 -7.46 1.0 148ms
16 -7.926861681873 + -14.57 -7.32 1.8 154ms
17 -7.926861681873 + -Inf -7.43 1.0 150ms
18 -7.926861681873 -15.05 -8.61 1.0 147ms
If we did not want to use AtomsBuilder we could of course use any other package which yields an AbstractSystem object. This includes:
Reading a system using AtomsIO
Read a file using AtomsIO, which directly yields an AbstractSystem.
using AtomsIO
system = load_system("Si.extxyz");Run the LDA calculation:
pseudopotentials = PseudoFamily("cp2k.nc.sr.lda.v0_1.semicore.gth")
model = model_DFT(system; pseudopotentials, functionals=LDA(), temperature=1e-3)
basis = PlaneWaveBasis(model; Ecut=15, kgrid=[4, 4, 4])
scfres = self_consistent_field(basis, tol=1e-8);n Energy log10(ΔE) log10(Δρ) Diag Δtime
--- --------------- --------- --------- ---- ------
1 -7.921712272711 -0.69 5.2 188ms
2 -7.926139799221 -2.35 -1.22 1.0 140ms
3 -7.926833238512 -3.16 -2.37 2.0 199ms
4 -7.926861263207 -4.55 -3.01 2.9 192ms
5 -7.926861655997 -6.41 -3.45 2.1 165ms
6 -7.926861674159 -7.74 -4.00 1.9 160ms
7 -7.926861677979 -8.42 -4.06 2.1 160ms
8 -7.926861679094 -8.95 -4.13 1.0 148ms
9 -7.926861681786 -8.57 -4.54 1.0 150ms
10 -7.926861681854 -10.17 -4.73 1.0 141ms
11 -7.926861681867 -10.91 -5.07 1.0 150ms
12 -7.926861681871 -11.40 -5.47 1.4 154ms
13 -7.926861681872 -11.78 -6.04 1.5 154ms
14 -7.926861681873 -12.67 -6.35 1.9 269ms
15 -7.926861681873 -13.85 -6.39 1.1 1.03s
16 -7.926861681873 -14.27 -6.95 1.0 141ms
17 -7.926861681873 + -Inf -7.04 1.5 151ms
18 -7.926861681873 -14.57 -8.37 1.0 141ms
The same could be achieved using ExtXYZ by system = Atoms(read_frame("Si.extxyz")), since the ExtXYZ.Atoms object is directly AtomsBase-compatible.
Directly setting up a system in AtomsBase
using AtomsBase
using Unitful
using UnitfulAtomic
# Construct a system in the AtomsBase world
a = 10.26u"bohr" # Silicon lattice constant
lattice = a / 2 * [[0, 1, 1.], # Lattice as vector of vectors
[1, 0, 1.],
[1, 1, 0.]]
atoms = [:Si => ones(3)/8, :Si => -ones(3)/8]
system = periodic_system(atoms, lattice; fractional=true)
# Now run the LDA calculation:
pseudopotentials = PseudoFamily("cp2k.nc.sr.lda.v0_1.semicore.gth")
model = model_DFT(system; pseudopotentials, functionals=LDA(), temperature=1e-3)
basis = PlaneWaveBasis(model; Ecut=15, kgrid=[4, 4, 4])
scfres = self_consistent_field(basis, tol=1e-4);n Energy log10(ΔE) log10(Δρ) Diag Δtime
--- --------------- --------- --------- ---- ------
1 -7.921716374329 -0.69 5.4 202ms
2 -7.926140719672 -2.35 -1.22 1.0 117ms
3 -7.926836978709 -3.16 -2.37 2.0 139ms
4 -7.926864638069 -4.56 -3.02 3.0 183ms
5 -7.926865067690 -6.37 -3.46 2.0 140ms
6 -7.926865086381 -7.73 -4.03 1.9 134ms
Obtaining an AbstractSystem from DFTK data
At any point we can also get back the DFTK model as an AtomsBase-compatible AbstractSystem:
second_system = atomic_system(model)FlexibleSystem(Si₂, periodicity = TTT):
cell_vectors : [ 0 5.13 5.13;
5.13 0 5.13;
5.13 5.13 0]u"a₀"
Atom(Si, [ 1.2825, 1.2825, 1.2825]u"a₀")
Atom(Si, [ -1.2825, -1.2825, -1.2825]u"a₀")
Similarly DFTK offers a method to the atomic_system and periodic_system functions (from AtomsBase), which enable a seamless conversion of the usual data structures for setting up DFTK calculations into an AbstractSystem:
lattice = 5.431u"Å" / 2 * [[0 1 1.];
[1 0 1.];
[1 1 0.]];
Si = ElementPsp(:Si, pseudopotentials)
atoms = [Si, Si]
positions = [ones(3)/8, -ones(3)/8]
third_system = atomic_system(lattice, atoms, positions)FlexibleSystem(Si₂, periodicity = TTT):
cell_vectors : [ 0 5.13155 5.13155;
5.13155 0 5.13155;
5.13155 5.13155 0]u"a₀"
Atom(Si, [ 1.28289, 1.28289, 1.28289]u"a₀")
Atom(Si, [-1.28289, -1.28289, -1.28289]u"a₀")