Relaxed Hartree-Fock (RxHF) Approach to use ab-initio Quantum Computation for Bigger Systems

The Application of ab-initio quantum theory is restricted for bigger systems due to huge computation
costs. In this work a new approach is described which allows us to apply an ab-initio quantum
method for bigger systems. It is shown that the dynamical electron correlation may be achieved by
relaxing Pauli’s exclusion principle partially. Thus, a restricted Hartree-Fock electron configuration
may be considered as a perturbed system of the exact configuration. Using this physical concept,
the matrix elements of the relaxation operators are constructed. Projecting this relaxation operator
on to Hartree-Fock wave function gives dynamical electron correlation energy directly. This method is
simple and implemented successfully for azulene and its chloride derivative to predict their absorption
spectra.