[Wannier] Unit of velocities in geninterp

[Vahid Askarpour]

Dear Giovanni,

Thank you for this clarification. I was using an earlier version (wannier90-2.0.1) and my geninterp output has the following header:

#  Kpt_idx   K_x (2pi/ang)     K_y (2pi/ang)     K_z (2pi/ang)     Energy (eV)      EnergyDer_x       EnergyDer_y       EnergyDer_z

I will switch to the latest version.

Best,
Vahid



On Mar 23, 2020, at 4:38 PM, Giovanni Pizzi <giovanni.pizzi at epfl.ch<mailto:giovanni.pizzi at epfl.ch>> wrote:

CAUTION: The Sender of this email is not from within Dalhousie.
Dear Vahid,
Thanks for noting this.

Note that the units of k-points in the output are 1/ang and not 2pi/ang.
Accordingly, the derivatives are in units of (eV * ang), you can verify checking with finite differences in a point with non-zero derivatives.

This will be included in the documentation in the next release.
https://github.com/wannier-developers/wannier90/pull/325

Best,
Giovanni


--
Giovanni Pizzi
Theory and Simulation of Materials and MARVEL, EPFL
http://people.epfl.ch/giovanni.pizzi
http://nccr-marvel.ch/en/people/profile/giovanni-pizzi

On 19 Mar 2020, at 11:28, Vahid Askarpour <vh261281 at dal.ca<mailto:vh261281 at dal.ca>> wrote:

Dear Wannier90 Users,

I have posted this on QE forum but the Wannier90 forum may be more appropriate.

In the postw90 folder, in file boltzwann.F90, it says,

\param deleig_k    array with the band derivatives at the given k point
                             (in eV * angstrom / (2pi) as internally given by the code)

So deleig_k is the electron velocity at a given k-point. When we set

geninterp=.true.
geninterp_alsofirstder=.true.

the postw90 output includes k-point coordinates (2pi/ang), energies (eV) and velocities (no units). Even the Wannier90 User guide does not specify the unit for velocities. Am I correct in assuming that these velocities are in eV*angstrom/(2pi)?

Thank you,
Vahid

Vahid Askarpour
Department of physics and atmospheric science
Dalhousie University
Halifax, NS
Canada
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