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
atom potentials : ElementPsp(Si, "/home/runner/.julia/artifacts/326db5c901e2681584ec5c06fc17f6c96e516ff9/Si.upf")
ElementPsp(Si, "/home/runner/.julia/artifacts/326db5c901e2681584ec5c06fc17f6c96e516ff9/Si.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 -7.921740348909 -0.69 5.8 212ms
2 -7.926133436589 -2.36 -1.22 1.0 132ms
3 -7.926833932231 -3.15 -2.37 2.0 156ms
4 -7.926861269652 -4.56 -3.01 3.1 193ms
5 -7.926861649307 -6.42 -3.42 1.9 156ms
6 -7.926861672154 -7.64 -3.92 1.8 149ms
7 -7.926861678967 -8.17 -4.12 1.9 224ms
8 -7.926861681770 -8.55 -4.84 1.1 804ms
9 -7.926861681847 -10.12 -5.08 2.1 153ms
10 -7.926861681866 -10.71 -5.50 1.6 142ms
11 -7.926861681872 -11.23 -6.06 1.0 134ms
12 -7.926861681873 -12.56 -6.87 2.1 154ms
13 -7.926861681873 -13.52 -6.99 2.2 179ms
14 -7.926861681873 + -14.75 -7.25 1.0 132ms
15 -7.926861681873 -14.75 -7.86 1.1 136ms
16 -7.926861681873 + -15.05 -8.76 2.2 157msIf 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 -7.921739399994 -0.69 5.5 201ms
2 -7.926132494813 -2.36 -1.22 1.0 133ms
3 -7.926834081155 -3.15 -2.37 2.1 170ms
4 -7.926861311870 -4.56 -3.01 2.8 181ms
5 -7.926861654260 -6.47 -3.46 2.4 161ms
6 -7.926861675208 -7.68 -4.01 1.6 146ms
7 -7.926861678244 -8.52 -4.08 1.9 149ms
8 -7.926861680783 -8.60 -4.32 1.0 130ms
9 -7.926861681809 -8.99 -4.78 1.2 137ms
10 -7.926861681866 -10.24 -5.10 1.8 150ms
11 -7.926861681871 -11.31 -5.92 1.2 140ms
12 -7.926861681873 -11.92 -6.30 2.5 166ms
13 -7.926861681873 -13.40 -6.29 1.4 142ms
14 -7.926861681873 -14.15 -6.98 1.0 137ms
15 -7.926861681873 -14.75 -7.57 1.6 145ms
16 -7.926861681873 + -14.75 -7.72 2.1 161ms
17 -7.926861681873 -15.05 -8.15 1.0 135msThe 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 -7.921702204417 -0.69 5.6 231ms
2 -7.926137879415 -2.35 -1.22 1.0 124ms
3 -7.926837293720 -3.16 -2.37 2.0 154ms
4 -7.926864670848 -4.56 -2.99 3.1 199ms
5 -7.926865052118 -6.42 -3.35 1.9 152ms
6 -7.926865079858 -7.56 -3.78 1.5 132ms
7 -7.926865090849 -7.96 -4.21 1.5 134msObtaining 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")