Extracting phonon velocity
Posted: Thu May 14, 2026 5:08 pm
Dear EPW users,
I am using EPW-5.4.1. To extract phonon velocities of Si (I am actually interested in the +/- sign of the velocity not the correct magnitude), I have added the following to the ephwann_shuffle.f90:
I ran the code on 100 q-points and for all the q-points, all the 6 x-components of velocity are identical. Different q-points have different velocities but each q-point has the same velocity for acoustic and optical modes. The routines in the latest EPW seems to be similar. Is this a bug in the code?
Thanks,
Vahid
Vahid Askarpour
Department of Physics and Atmospheric Science
Dalhousie University
Halifax, Canada
I am using EPW-5.4.1. To extract phonon velocities of Si (I am actually interested in the +/- sign of the velocity not the correct magnitude), I have added the following to the ephwann_shuffle.f90:
Code: Select all
CALL vmewan2blochp(xxq, nmodes, nrr_q, irvec_q, ndegen_q, uf, vmefp(:, :, :), wf(:, qind), rws, nrws)
DO imode = 1, nmodes
vmeq_av(:) = zero
DO jmode = 1, nmodes
vmeq_av(:) = vmeq_av(:) + REAL(vmefp(:, jmode, jmode), KIND = DP)
ENDDO
vmeqf(:, imode) = vmeq_av(:)
ENDDO
write(99,'(6E26.16E3)') vmeqf(1,1), vmeqf(1,2), vmeqf(1,3), vmeqf(1,4), vmeqf(1,5), vmeqf(1,6)
Thanks,
Vahid
Vahid Askarpour
Department of Physics and Atmospheric Science
Dalhousie University
Halifax, Canada