# EXTERNAL_DENSITY

References: Zhao1994, Tozer1996

Section for the use of the ZMP technique on external densities. [Edit on GitHub]

## Keywords

- FERMI_AMALDI

- FILE_DENSITY

- LAMBDA

- ZMP_CONSTRAINT

## Keyword descriptions

FERMI_AMALDI: logical = T

  Lone keyword: `T`

  Usage: FERMI_AMALDI <LOGICAL>

  Add the Fermi-Amaldi contribution to the Hartree potential. It leads to a more stable convergence. [Edit on GitHub]

FILE_DENSITY: string[ ] = RHO_O.dat

  Usage: FILE_DENSITY <FILENAME>

  Specifies the filename containing the target density in *.cube format. In the MGRID section it must be imposed NGRID 1, as it works with only one grid. The number of points in each direction, and the spacing must be previously defined choosing the plane waves cut-off in section MGRID keyword CUTOFF, and the cube dimension in section SUBSYS / CELL / keyword ABC [Edit on GitHub]

LAMBDA: real = 1.00000000E+001

  Usage: LAMBDA <REAL>

  Lagrange multiplier defined in the constraint ZMP method. When starting, use small values when starting from scratch (around 5,10). Then gradually increase the values depending, restarting from the previous calculation with the smaller value. To choose the progressive values of LAMBDA look at the convergence of the eigenvalues. [Edit on GitHub]

ZMP_CONSTRAINT: enum = COULOMB

  Usage: ZMP_CONSTRAINT <CHAR>

  Valid values:

  - `COULOMB` Coulomb constraint, integral of [rho_0(r)-rho(r)]/|r-r’|

  - `DIFF` Simple constraint, [rho_0(r)-rho(r)]

  - `NONE` No constrain imposed

  Specify which kind of constraint to solve the ZMP equation. The COULOMB default option is more stable. [Edit on GitHub]