# Recursion

This page gives hints on how to perform orbital-free calculations with the ABINIT package.

## Introduction¶

It is possible to use Thomas-Fermi kinetic functional (explicit functional of the density) or Thomas-Fermi-Weizsacker kinetic functional (with Gradient Corrections) instead of Kohn-Sham kinetic energy functional (implicit functional of the density through Kohn-Sham wavefunctions).
See [Perrot1979].
The Recursion Method may be used in order to compute electronic density, entropy, Fermi energy and eigenvalues energy. This method computes the density without computing any orbital, is efficient at high temperature, with a efficient parallelization (almost perfect scalability).

At present, it only works for local pseudopotentials, severely restricting the use of this method.

compulsory:

• tfkinfunc Thomas-Fermi KINetic energy FUNCtional

basic:

• rectolden RECursion - TOLerance on the difference of electronic DENsity

useful:

• recefermi RECursion - initial guess of the FERMI Energy
• recgratio RECursion - Grid RATIO
• recrcut RECursion - CUTing Radius
• tfw_toldfe Thomas-Fermi-Weizsacker: TOLerance on the DiFference of total Energy, for initialization steps

expert:

• recnpath RECursion - Number of point for PATH integral calculations
• recnrec RECursion - Number of RECursions
• recptrott RECursion - TROTTer parameter
• rectesteg RECursion - TEST on Electron Gas

internal:

mpiio:

v4:

v5:

v7:

v8: