Experiment 3.5 Hartree-Fock Calculations and

EXPERIMENT 3.5 HARTREE-FOCK CALCULATIONS AND STRUCTURE PREDICTIONS USING SIMPLIFIED BROWN AND GREEN N,N -DISALICYLALDEHYDE-1,3-PROPANEDIIMINENICKEL(ll), [Ni(salpd)], COMPLEXES 

In recent years, dramatic advances in computational power combined with the marketing of packaged computational chemistry codes have allowed quantum chemical calculations to become fairly routine in both prediction and verification of experimental observations. The 1998 Nobel Prize in Chemistry reflected this impact by awarding John A. Pople a shared prize for his development of computational methods in quantum chemistry. The Hartree-Fock approximation is a basic approach to the quantum chemical problem described by the Schrodinger equation, equation (3.10), where the Hamiltonian (//) operating on the wavefunction OP) yields the energy (E) multiplied by the wavefunction. 

Closed-shell (diamagnetic) systems can be investigated using a restricted Hartree-Fock (RHF) calculation, while unrestricted Hartree-Fock (UHF) calculations are able to accommodate open-shell (paramagnetic) systems as well. The Hartree-Fock approximation is also important in serving as a foundation for a variety of more accurate quantum chemical calculations that account for electron correlation. 

If a geometry optimization is being performed, a complete SCF convergence will be performed for a fixed set of atomic coordinates then the atomic coordinates will be updated and a new SCF cycle will be performed. This series of SCF cycles, each with updated atomic coordinates, continues until the present geometry tolerance criteria are met. Generally, post-calculation analyses are performed at this point, when the calculation is converged both for the final SCF cycle as well as the geometry optimization. 

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EXPERIMENT 3.5 HARTREE-FOCK CALCULATIONS AND STRUCTURE PREDICTIONS 69... 

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