Loading QP corrections

Databases from previous runs are automatically loaded loaded by simply pointing yambo to the folder which contains them. As an example, if I compute the static screening of a material

$yambo -F screening.in -J em1s -C em1s

The ndb.em1s database will be created and put inside the bse folder. This can be later used in the bse run by running

$yambo -F bse.in -J "bse,em1s" -C bse

The situation with the ndb.QP database is different can be computed with a given SAVE folder and later used with another one. This is particularly useful when computing QP correction on a coarse k-points grid, and later using them on a finer kpt grid, for example for computing optical properties within BSE. As a consequence, the QP corrections computed with the yambo code are loaded by setting a dedicated variable in the input file

KfnQPdb= "E < 02_QP/ndb.QP uki"

The "uki" string controls the way in which the qp corrections are interpolated from the coarser to the finer grid. The default and means nearest kpt interpolation. However you can change it.

There are 4 available options:
- Number 4: Nearest K interpolation ("ui" or "uki") [default]
- Number 5: Nearest E interpolation ("uei")
- Number 6: Fourier K interpolation ("ubi")
- Number 7: Fit energie with shissor + stretching and use this to get the other values (fit)

Options 4 and 6 can be reproduced by ypp. There are also two extra control options (that you also find in ypp)

KfnQP_INTERP_NN= 1 [default] (number of NN considered, valid for 4)
KfnQP_INTERP_shells= XX (number of shells used, valid for 6 )