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   -7.916436036810                   -0.69    4.5    102ms
  2   -7.921205765518       -2.32       -1.52    1.0   51.3ms
  3   -7.921403165242       -3.70       -2.49    1.4   55.0ms
  4   -7.921440928302       -4.42       -2.81    2.5   72.6ms
  5   -7.921441556083       -6.20       -2.95    1.1   61.1ms
  6   -7.921442007147       -6.35       -4.50    1.0   81.9ms
  7   -7.921442021768       -7.84       -4.57    3.0   80.1ms
  8   -7.921442022126       -9.45       -5.34    1.0   51.0ms
  9   -7.921442022143      -10.76       -6.13    1.9   59.9ms
 10   -7.921442022144      -12.16       -6.12    2.1   66.1ms
 11   -7.921442022144      -12.81       -6.74    1.0   60.8ms
 12   -7.921442022144      -14.05       -7.18    1.1   52.3ms
 13   -7.921442022144   +    -Inf       -7.48    1.2   55.1ms
 14   -7.921442022144   +    -Inf       -8.03    1.0   59.4ms

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]);

119.131391 seconds (108.95 M allocations: 101.975 GiB, 9.19% gc time, 0.30% compilation time: 100% of which was recompilation)

These are the final phonon frequencies:

phret_q0.frequencies

6-element Vector{Float64}:
 -0.0034981553586915294
 -0.002977451163635512
 -0.00297745116313852
  0.0043022306402171
  0.004302230640266441
  0.004353201770872342