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   -7.916456098405                   -0.69    4.6    102ms
  2   -7.921208929673       -2.32       -1.52    1.0   50.7ms
  3   -7.921403835683       -3.71       -2.49    1.2   53.1ms
  4   -7.921440860463       -4.43       -2.82    2.6   71.1ms
  5   -7.921441556003       -6.16       -2.96    1.0   58.7ms
  6   -7.921442005493       -6.35       -4.47    1.0   50.2ms
  7   -7.921442021610       -7.79       -4.50    2.9   77.7ms
  8   -7.921442022120       -9.29       -5.16    1.0   50.6ms
  9   -7.921442022142      -10.66       -5.57    1.4   55.7ms
 10   -7.921442022143      -11.89       -5.85    1.6   65.0ms
 11   -7.921442022144      -12.18       -7.30    1.0   52.3ms
 12   -7.921442022144      -13.40       -7.63    3.0   79.1ms
 13   -7.921442022144      -14.75       -7.40    1.0   51.3ms
 14   -7.921442022144   +    -Inf       -8.70    1.0   58.0ms

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]);

111.315994 seconds (107.35 M allocations: 102.086 GiB, 7.21% gc time, 0.31% compilation time: 100% of which was recompilation)

These are the final phonon frequencies:

phret_q0.frequencies

6-element Vector{Float64}:
 -0.0034981553599279336
 -0.0029774511620988616
 -0.0029774511619724458
  0.004302230630767245
  0.004302230630981391
  0.0043532017608360375