In order to use different GGA approximations of the non-additive
kinetic potential, the flag
-k string must be used.
Here string is the acronym used to identify a given GGA
kinetic energy approximation, that can be selected among the following
revapbek: generalized gradient approximation with a PBE-like enhancement factor, obtained using the asymptotic expansions of the semiclassical neutral atom as reference [145,146] (revAPBEk). This is the default choice;
lc94: Perdew-Wang (PW91) exchange functional reparametrized for kinetic energy by Lembarki and Chermette  (LC94);
t-f: gradient expansion truncated at the zeroth order (GEA0), corresponding to the Thomas-Fermi functional.
For example, the command
FDE -p 3 -k lc94approximates the non-additive kinetic contribution to the embedding potential through the functional derivative of LC94 kinetic energy functional.
A pure electrostatic embedding can be also performed with
script, where the embedding potential required by a subsystem A
to account for the presence of the B one will be merely:
FDE -p 3 -k electroand can be performed for both Kohn-Sham (only for LDA/GGA exchange-correlation functionals) and Hartree-Fock methods.
The electrostatic embedding is implemented only for testing purpose. It resembles an electrostatic embedding with external point-charges and/or point-dipoles, but it is ``exact'' as it is based on the whole densities (i.e. it considers all multipole moments of the density and the polarizabilies at all orders).