In theory, the @eplf can be computed from any kind of wave function (but note
that the present code is written in the Restricted Hartree-Fock framework).
The first step is to calculate a wave function using a quantum
chemistry code. Then, the parameters of the wave function need to be saved in
the @ezfio database in order to be communicated to the @exe fortran program.

@section Wave function preparation

@macro gamess
{@acronym{GAMESS} }
@end macro

@macro mcscf
{@acronym{MCSCF} }
@end macro

@macro scf
{@acronym{SCF} }
@end macro

@macro cas
{@acronym{CAS-SCF} } 
@end macro

@macro rhf
{@acronym{RHF} } 
@end macro

@macro ci
{@acronym{CI} } 
@end macro

Wave functions calculated using Gaussian, Molpro and @gamess can be read from
the output files.  A major constraint is to realize a @emph{single point} 
calculation, all the following quantities appearing in the output file:
@itemize
@item The basis set
@item The full set of MOs
@item The coefficients of the Slater determinant expansion for @ci wave functions.
@end itemize

@subsection Using Gaussian

In the Gaussian input file, use the keywords @code{GFPRINT} and @code{pop=Full}.
In the case of @cas wave functions, use the @code{#p} keyword and the @code{SlaterDet}
attribute of the @code{CAS} keyword.
When doing a @cas with Gaussian, first do the Hartree-Fock calculation saving the checkpoint
file and then do the @cas in a second step.

@subsection Using Molpro

Use the following options in the Molpro input file:
@itemize @bullet
@item @code{print,basis;} 
@item @code{gprint,civector;}
@item @code{gprint,orbital;}
@item @code{gthresh,printci=0.;} for @mcscf calculations
@end itemize

An @rhf calculation is mandatory before any @mcscf calculation, since some
information is printed only the @rhf part. Be sure to print @emph{all} molecular
orbitals using the @code{orbprint} keyword, and to use the same spin multiplicity
and charge between the @rhf and the @cas.

@subsection Using @gamess

For @mcscf calculations, first compute the @mcscf single-point wave function
with the @acronym{GUGA} algorithm. Then, put the the @mcscf orbitals (of the
@code{.dat} file) in the @gamess input file, and run a single-point
@acronym{GUGA} @ci calculation with
the following keywords:
@itemize @bullet
@item
@code{PRTTOL=0.0001} in the @code{$GUGDIA} group to use a threshold of @math{10^{-4}} on
the @ci coefficients
@item
@code{NPRT=2} in the @code{$CIDRT} group to print the CSF expansions in terms of Slater determinants
@item
@code{PRTMO=.T.} in the @code{$GUESS} group to print the molecular orbitals
@end itemize


@subsection Using your own code
Any other code producing a wave function can be used, as long as you are able to gather all
the needed data.