Negative scattering rates
Posted: Tue Nov 16, 2021 6:40 pm
Dear EPW users,
When calculating the momentum relaxation time using the following line in the transport.f90 of QE-6.8
and later
If vkq is larger than vkk, it is possible that Eq. 1 gives a value larger than 1 for certain kpoints.
Eq. 2 then makes the final vel_factor negative which in turn makes the scattering rates for those kpoints negative.
Is there a way these negative rates could be avoided?
One possible solution is to use the following instead of Eq. 1
Eq. 3 will guarantee that vel_factor is never larger than 1.
I would appreciate any input in this matter.
Thank you,
Vahid
Vahid Askarpour
Department of physics and atmospheric science
Dalhousie University
Halifax, NS
CANADA
When calculating the momentum relaxation time using the following line in the transport.f90 of QE-6.8
Code: Select all
vel_factor(ibnd, jbnd) = DDOT(3, vkk(:, ibnd), 1, vkq(:, jbnd), 1) / &
DDOT(3, vkk(:, ibnd), 1, vkk(:, ibnd), 1) (Eq. 1)
Code: Select all
vel_factor(:, :) = one - vel_factor(:, :) (Eq. 2)
Eq. 2 then makes the final vel_factor negative which in turn makes the scattering rates for those kpoints negative.
Is there a way these negative rates could be avoided?
One possible solution is to use the following instead of Eq. 1
Code: Select all
vel_factor(ibnd,jbnd) = DDOT(3, vkk(:,ibnd), 1,vkq(:,jbnd), 1) / &
(abs(SQRT(DDOT(3, vkk(:,ibnd), 1,vkk(:,ibnd),1)))* &
abs(SQRT(DDOT(3, vkq(:,jbnd), 1,vkq(:,jbnd),1))) ) (Eq. 3)
I would appreciate any input in this matter.
Thank you,
Vahid
Vahid Askarpour
Department of physics and atmospheric science
Dalhousie University
Halifax, NS
CANADA