  The configuration interaction (CI) is a versatile wavefunction theory for
interacting fermions but it involves an extremely long CI series. Using a
symmetric tensor decomposition (STD) method, we convert the CI series into a
compact and numerically tractable form. The converted series encompasses the
Hartree-Fock state in the first term and rapidly converges to the full-CI
state, as numerically tested using small molecules. Provided that the length of
the STD-CI series grows only moderately with the increasing complexity of the
system, the new method will serve as one of the alternative variational methods
to achieve full-CI with enhanced practicability.
