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   -7.916436960214                   -0.69    4.6    104ms
  2   -7.921211273820       -2.32       -1.52    1.0   52.9ms
  3   -7.921404784852       -3.71       -2.49    1.2   55.6ms
  4   -7.921440957223       -4.44       -2.82    2.6   75.9ms
  5   -7.921441619373       -6.18       -3.00    1.0   53.5ms
  6   -7.921442007697       -6.41       -4.55    1.1   55.4ms
  7   -7.921442021760       -7.85       -4.58    3.0   83.6ms
  8   -7.921442022125       -9.44       -5.27    1.0   64.1ms
  9   -7.921442022143      -10.73       -5.92    1.4   60.9ms
 10   -7.921442022144      -12.16       -5.99    2.1   70.8ms
 11   -7.921442022144      -12.49       -6.67    1.0   55.9ms
 12   -7.921442022144      -13.75       -7.04    1.5   62.1ms
 13   -7.921442022144      -14.57       -7.44    1.2   66.7ms
 14   -7.921442022144      -15.05       -8.47    1.1   59.9ms

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]);

117.023536 seconds (107.41 M allocations: 102.016 GiB, 9.48% gc time, 0.00% compilation time)

These are the final phonon frequencies:

phret_q0.frequencies

6-element Vector{Float64}:
 -0.003498155362967933
 -0.0029774511670800333
 -0.00297745116658925
  0.0043022306303090105
  0.004302230630822649
  0.004353201761507754