EPW Forum

Dear EPW Community, In transport.f90, the transition probability is defined as ! transition probability ! (2 pi/hbar) * (k+q-point weight) * g2 * ! { [f(E_k+q) + n(w_q)] * delta[E_k - E_k+q + w_q] + ! [1 - f(E_k+q) + n(w_q)] * delta[E_k - E_k+q - w_q] } The first term is absorption (+w_q) and the se...

Dear H. Lee, I changed the q-grid to 12x12x12, matching the k-grid. The electron and phonon dispersions from EPW match those of QE. The PSP is norm-conserving. After some digging into the code, I believe the mismatch between emission and absorption coupling constant comes from the phase factor exp(i...

Dear H. Lee, I am using a norm-conserving PSP. The coarse k-grid is 12x12x12 and q-grid is 6x6x6. These give converged EPW band structure and phonon dispersion relative to QE counterparts. I was expecting some differences in g2 but not a factor of 100. I will dig further into the code. There might b...

Dear EPW community, I am studying the following emission/absorption pair in silicon: I start with a single k-point (0.0 0.3 0.3) and a single q-point (0.0 0.1 0.1). My kq-point is (0.0 0.4 0.4). I print g2 from transport.f90. For mode #6, g2=9.51E-9. Then I use k-point (0.0 0.4 0.4) and q-point (0.0...

Dear H. Lee,

Thank you for your response. Upto qe-6.7MAX, the factor 2 is included in the velocity expression. Only 6.8 and 7.0 have removed the 2.

Thanks,
Vahid

Since there has been no response, is it safe to assume that one of those versions is incorrect?

Thanks,
Vahid

Dear EPW Community,

In the QE-6.0 version of EPW, dipole velocity was defined as
In the latest version, the factor 2 is missing. Are both correct?

Thank you,
Vahid

Vahid Askarpour
Dalhousie University
Halifax, Canada

Dear EPW users, When calculating the momentum relaxation time using the following line in the transport.f90 of QE-6.8 vel_factor(ibnd, jbnd) = DDOT(3, vkk(:, ibnd), 1, vkq(:, jbnd), 1) / & DDOT(3, vkk(:, ibnd), 1, vkk(:, ibnd), 1) (Eq. 1) and later vel_factor(:, :) = one - vel_factor(:, :) (Eq. 2) I...

Dear Samuel,

Thank you for this clarification.

Best wishes,
Vahid

Hi hlee,

Thank you for this clarification.

Best,
Vahid