12	Ab initio Method/First Principle Calculation		Based on Solution of Schrödinger Equation	Works well for H atom only. For all other atoms, approximations are needed	Robert Parr (Caltech)	1950	[288]
13	Hartree Fork Method and Slater Determinant		Uses the variational theorem (which is wavefunction based approach using mean field approximation)	Approximate solution is obtained. It is a form of Ab initio method.			[289]
14	Evolution of Hartree Fork Method	Self-Constrained Field (SCF) Method	Evolution of HF Method	Approximate solutions			[289]
		Møller-Plesset (MP) perturbation (MP 1)	Hamiltonian is divided into two parts $\hat{H} = {\hat{H}}_{0} + λ \hat{V}$ and solved	ψ and energy are HF ψ and HF energy			[289]
		MP 2	ψ remain same, energy is changed	ψ is treated by the help of summations			[289]
		Density Functional Theory (DFT)	Energy of system is obtained from electron density	Approximation based		1996	[290] [291] [292]
15	Interatomic Potential		Explain Interaction of atoms in a system in terms of potentials	Limited by Accuracy, Transferability and Computational Speed of System	Multi (Many) Body Potentials Daw Baska (Sandia National Labs)	1984	[293]