# functional keywords

XC-functional parameters

## functional.list

List of exchange-correlation functional used in the calculation. Any
number of exchange-correlation functionals can be listed. A list of the
functionals may be found on the [LibXC
website](http://www.tddft.org/programs/octopus/wiki/index.php/Libxc_functionals).

**type**: `cell array of strings`

**default**: `{'XC_LDA_X','XC_LDA_C_PW'}`

**example**: `functional.list = {'XC_GGA_X_PBE','XC_GGA_C_PBE'`

## functional.libxc

Use LibXC wrapper if functional.libxc = true; most functionals may only
be used if functional.libxc = true, only
{\'XC_LDA_X\',\'XC_LDA_C_PW\',\'XC_GGA_X_PBE\',\'XC_GGA_C_PBE\'} may be
listed if functional.libxc = false.

**type**: `scalar`

**default**: `false`

**allowed**: `true,false`

**example**: `functional.libxc = true`

## functional.isrelativistic

Use relativistic implementation of
{\'XC_LDA_X\',\'XC_LDA_C_PW\',\'XC_GGA_X_PBE\',\'XC_GGA_C_PBE\'}

**type**: `scalar`

**default**: `false`

**allowed**: `true,false`

**example**: `functional.isrelativistic = true`

## functional.mbjLim

Certain materials (e.g. 2D material) have a very low density in certain
regions. The MBJ routines break and leads unphysical results in those
regions. The parameter mbjLim tells RESCU to use regular LDA exchange in
regions that have a density below mbjLim.

**type**: `scalar`

**default**: `0`

**example**: `functional.mbjLim = 1e-3`

## functional.mbjc

Value of the c parameter in Tran & Blaha\'s MBJ09 functional. It is
calculated by default.

**type**: `scalar`

**example**: `functional.mbjc = 1.13`

## functional.includeU

Determines whether to include Hubbard-type interactions.

**type**: `scalar`

**default**: `false`

**allowed**: `true,false`

**example**: `functional.includeU = true`
