LTWO CENTER

LTWO_CENTER = [logical]
Default: LTWO_CENTER = .FALSE. 

Description: LTWO_CENTER calculates off-center Coulomb integrals.

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When chosen, the system calculates two types of integrals:

• Bare integrals (stored in VRijkl)

[math]\displaystyle{ V_{ijkl}^{\sigma\sigma'} = \int {\rm d}{\bf r}\int {\rm d}{\bf r}' \frac{w_{i}^{*\sigma}({\bf r}) w_{j}^{\sigma}({\bf r}) w_{k}^{*\sigma'}({\bf r}'+{\bf R}) w_{l}^{\sigma'}({\bf r}'+{\bf R})}{|{\bf r}-{\bf r}'|} }[/math]

• Effectively screened integrals (stored in URijkl)

[math]\displaystyle{ 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}) }[/math]

When chosen, cRPA matrix elements in vaspout.h5 can be used with py4vasp to analyze the spatial decay of the Coulomb interaction using the Ohno potential

[math]\displaystyle{ U(R) = \frac{U(R=0)}{\sqrt{\frac{R}\delta + 1}} }[/math]

import py4vasp as pv

calc = pv.Calculation.from_path(".")
calc.effective_coulomb.plot(selection="U V", radius=...)

The above plots the spatial decay of the Coulomb interaction and fits the Ohno potential to the off-center integrals. Using radius=... passes the radial grid directly from the VASP output.

Mind: Available as of VASP 6.6.0

Related tags and articles

VRijkl, URijkl, LDISENTANGLED, LWEIGHTED, LSCRPA, ALGO

Workflows that use this tag