calcium_4s = SlaterOrbital(
    principal_quantum_number=4,
    angular_momentum=0,
    slater_coefficients=[ 1.067*1/Bohr ],
    weights=[ 1.0 ]
    )

calcium_4p = SlaterOrbital(
    principal_quantum_number=4,
    angular_momentum=1,
    slater_coefficients=[ 0.893*1/Bohr ],
    weights=[ 1.0 ]
    )

calcium_3d = SlaterOrbital(
    principal_quantum_number=3,
    angular_momentum=2,
    slater_coefficients=[ 1.906*1/Bohr ],
    weights=[ 1.0 ]
    )

CalciumBasis = HuckelBasisParameters(
    element=PeriodicTable.Calcium,
    orbitals=[ calcium_4s , calcium_4p , calcium_3d ],
    occupations=[ 0.222222222222 , 0.666666666667 , 1.11111111111 ],
    ionization_potential=[ -5.321*eV , -3.573*eV , -3.337*eV ],
    onsite_hartree_shift=[ 9.0*eV , 9.0*eV , 9.0*eV ],
    onsite_spin_split=[[-0.3226, -0.2217, -0.16475], [-0.2217, -0.2274, -0.09838], [-0.16475, -0.09838, -0.2542]]*eV,
    wolfsberg_helmholtz_constant=1.75,
    vacuum_level=0.0*eV,
    )