# Calculating the q resolved Eliashberg function

Hi,

I’m trying to calculate the q resolved Eliashberg function on a grid of q-points in the BZ, which is a thing I’ve seen done in various papers with Wannier interpolation in QE+W90, but I was wondering if it is possible to do in Abinit with the new eph code.

I tried to follow the tutorial, from what I understand the q dependent Eliashberg function is stored in the A2F.nc file, but I’m having trouble extracting the data from this file. Usually I read NetCDF files with Matlab, but in this case I’m struggling with understanding the meaning of the quantities contained in the A2F.nc file. I would have expected to just find a vector containing the reduced coordinates of the q-points and another vector of the same size containing the values of alpha^2F in those points, but it doesn’t look like that to me. Can anybody give me some insight?

Thanks,
Luca

Hi Luca,

the file contains several different versions of a2F, but not q resolved. They are calculated on different q grids, with and without interpolation (qintp and qcoarse resp.)
Should be easy to add as an output option, but it’s not done afaik.

In the log/ouput files there are mode and q presentations of the lambda and line width values, for the original input q points. Might be a start for your analysis.

best

Matthieu

Hi Matthieu,

thanks for your reply. So, for example, if I take one version of a2F, it looks like the netcdf file contains these 3 arrays of data

``````    a2ftr_mesh_qintp
Size:       473x1
Dimensions: a2ftr_nomega_qintp
Datatype:   double
a2ftr_values_qintp
Size:       473x3x3x4x1
Dimensions: a2ftr_nomega_qintp,three,three,natom3p1,number_of_spins
Datatype:   double
a2ftr_lambdaw_qintp
Size:       473x3x3x4x1
Dimensions: a2ftr_nomega_qintp,three,three,natom3p1,number_of_spins
Datatype:   double
``````

could you help me understand what they are? I wasn’t able to find any documentation on the Abinit website about this.

Luca

Note that a2ftr is for transport calculations (see the corresponding tutorials and papers by PB Allen). The 3x3 matrix versions are tensors wrt electron group velocities. I think the 3natom+1 dimension is a phonon band decomposition, plus the total. Lambdaw is related to values the way the epc superconducting lambda is related to the linewidths gamma