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   -7.916449541161                   -0.69    4.8    101ms
  2   -7.921209888401       -2.32       -1.52    1.0   49.1ms
  3   -7.921403655405       -3.71       -2.49    1.2   52.0ms
  4   -7.921440985979       -4.43       -2.82    2.6   71.2ms
  5   -7.921441557171       -6.24       -2.95    1.1   50.9ms
  6   -7.921442007292       -6.35       -4.49    1.0   49.8ms
  7   -7.921442021739       -7.84       -4.56    3.0   89.6ms
  8   -7.921442022128       -9.41       -5.24    1.0   50.2ms
  9   -7.921442022143      -10.83       -6.05    1.4   54.7ms
 10   -7.921442022144      -12.07       -5.97    2.1   65.9ms
 11   -7.921442022144      -12.52       -6.87    1.0   50.8ms
 12   -7.921442022144      -14.15       -7.08    1.2    134ms
 13   -7.921442022144      -14.75       -7.35    1.0   59.6ms
 14   -7.921442022144   +  -15.05       -8.21    1.1   52.2ms

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]);

113.606321 seconds (109.10 M allocations: 102.234 GiB, 8.60% gc time, 0.29% compilation time: 100% of which was recompilation)

These are the final phonon frequencies:

phret_q0.frequencies

6-element Vector{Float64}:
 -0.003498155360712817
 -0.002977451163861268
 -0.0029774511635105847
  0.004302230634527601
  0.004302230635236202
  0.004353201765385476