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Phonon computations¶

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

In [1]:

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);
nothing  # hide

n     Energy            log10(ΔE)   log10(Δρ)   Diag   Δtime
---   ---------------   ---------   ---------   ----   ------
  1   -7.916435700389                   -0.69    4.8    508ms
  2   -7.921206001831       -2.32       -1.52    1.0   50.3ms
  3   -7.921405819539       -3.70       -2.49    1.4   55.1ms
  4   -7.921440921267       -4.45       -2.83    2.5   71.5ms
  5   -7.921441656914       -6.13       -3.03    1.1   53.1ms
  6   -7.921442008158       -6.45       -4.53    1.0   57.1ms
  7   -7.921442021682       -7.87       -4.54    2.9   85.9ms
  8   -7.921442022123       -9.36       -5.25    1.0   58.8ms
  9   -7.921442022143      -10.69       -6.03    1.6   62.0ms
 10   -7.921442022144      -12.16       -6.07    2.1   88.5ms
 11   -7.921442022144      -12.71       -6.60    1.0   51.4ms
 12   -7.921442022144      -13.97       -7.03    1.2   53.6ms
 13   -7.921442022144      -14.75       -7.70    1.1   52.8ms
 14   -7.921442022144   +  -14.57       -8.12    1.8    108ms

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

In [2]:

scfres = DFTK.unfold_bz(scfres)
phret_q0 = @time DFTK.phonon_modes(scfres; q=[0.25, 0.25, 0.25]);
nothing  # hide

152.797460 seconds (159.01 M allocations: 104.604 GiB, 7.43% gc time, 25.39% compilation time)

These are the final phonon frequencies:

In [3]:

phret_q0.frequencies

Out[3]:

6-element Vector{Float64}:
 -0.0034981553613516723
 -0.0029774511663139334
 -0.0029774511660595397
  0.004302230638734129
  0.004302230638938137
  0.00435320176869754