hamiltonian to be employed in self-energy calculations. Used in conjonction with 'pt_density_matrix' or with 'read_fchk' or read an existing DENSITY_MATRIX file.</li><br>
<hr>
<a name=virtual_fno><li>                 <span style="display:inline-block;background:#EEEEEE;width:400px">               <b>virtual_fno</b>  </span>  
<br><br>
<i>Optional</i><br>
Default: no<br><br>
Activates the Frozen Natural Orbitals technique to span the virtual orbitals subspace with fewer orbitals. The dimension of the space i