Phonon computations

This is a quick sketch how to run a simple phonon calculation using DFTK. First we run an SCF calculation.

using AtomsBuilder
using DFTK
using PseudoPotentialData

pseudopotentials = PseudoFamily("cp2k.nc.sr.lda.v0_1.semicore.gth")
model  = model_DFT(bulk(:Si); pseudopotentials, functionals=LDA())
basis  = PlaneWaveBasis(model; Ecut=10, kgrid=[4, 4, 4])
scfres = self_consistent_field(basis, tol=1e-8);

n     Energy            log10(ΔE)   log10(Δρ)   Diag   Δtime
---   ---------------   ---------   ---------   ----   ------
  1   -7.916399484911                   -0.69    4.6    107ms
  2   -7.921197328461       -2.32       -1.52    1.0   63.3ms
  3   -7.921400952127       -3.69       -2.49    1.4   53.0ms
  4   -7.921440824058       -4.40       -2.81    2.8   70.7ms
  5   -7.921441532189       -6.15       -2.95    1.0   49.2ms
  6   -7.921442002958       -6.33       -4.42    1.0   58.2ms
  7   -7.921442021703       -7.73       -4.54    2.9   76.6ms
  8   -7.921442022124       -9.38       -5.19    1.0   49.9ms
  9   -7.921442022131      -11.21       -5.11    1.8   57.8ms
 10   -7.921442022143      -10.90       -5.79    1.0   50.0ms
 11   -7.921442022144      -12.12       -6.92    1.1   57.6ms
 12   -7.921442022144      -13.32       -6.49    2.8   72.0ms
 13   -7.921442022144      -13.82       -7.39    1.0   50.3ms
 14   -7.921442022144      -14.75       -8.08    1.6    240ms

Next we compute the phonon modes at the q-point [1/4, 1/4, 1/4].

scfres = DFTK.unfold_bz(scfres)
phret_q0 = @time DFTK.phonon_modes(scfres; q=[0.25, 0.25, 0.25]);

107.449567 seconds (110.19 M allocations: 102.050 GiB, 7.34% gc time, 0.00% compilation time)

These are the final phonon frequencies:

phret_q0.frequencies

6-element Vector{Float64}:
 -0.00349815535484936
 -0.00297745115424265
 -0.0029774511536448957
  0.004302230626879498
  0.004302230627075558
  0.004353201756931132