URijkl

Mind: Available as of VASP.6.5.2.

This file stores the effectively screened off-centre Coulomb integrals

$U_{ijkl}^{\sigma\sigma'} = \int {\rm d}{\bf r}\int {\rm d}{\bf r}' w_{i}^{*\sigma}({\bf r}) w_{j}^{\sigma}({\bf r}) U({\bf r},{\bf r}',\omega) w_{k}^{*\sigma'}({\bf r}'+{\bf R}) w_{l}^{\sigma'}({\bf r}'+{\bf R})$

The format is as follows:

# U_ijkl = [ij,R|kl,0] 
#  I   J   K   L          RE(V_IJKL)          IM(V_IJKL)
# R:    1  0.000000  0.000000  0.000000
   1   1   1   1        4.3457689208        0.0000000000
   2   1   1   1        0.0000021313        0.0000001349
... 
# R:    2  0.000000  0.000000  1.000000
   1   1   1   1        1.2535567886        0.0000000000
   2   1   1   1        0.0324545667       -0.0000455665
 ...

The Coulomb integrals are computed and written as a post-processing step using ALGO=2e4wa. The process differs for two types of integrals:

• VRijkl (bare off-centre Coulomb integrals): Always written when requested.
• URijkl: Only written if all WFULLxxxx.tmp files matching the selected k-point grid are present in the working directory.

The basis set for these calculations can be specified using the DMFT_BASIS tag.

Evaluating Coulomb integrals can be computationally intensive, especially when dealing with a large number of basis functions.

Tip: To improve performance, you can use a coarser sub-grid of the original k-point grid by enabling the LDOWNSAMPLE tag.

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