Theoretical Chemistry Essay

Theoretical chemistry is an insightful mathematical tool to understand experimental facts and provide conceptual directions to experimentalists. The discovery of theoretical concepts came after several experimentations and attempts. Earlier progress of theoretical chemistry was narrowed due to the limitation of computational facility. The growth in the empower of electronic computers and softwares have increased the inability to unfold the problems of vigorous calculations into easier forms and enabled to emergence of computational chemistry.1,2 In recent years, it has become a branch of science and now it interfaces connection between chemistry, physics, mathematics, biology and computer science and it provides an idea to solve electronic properties. Quantum chemistry is one of the suitable methodologies for computational chemistry to compute

According to the variational theorem for the ground state ‘the energy calculated from a trial wave function will always be greater than the true energy’. Therefore to obtain lower energy one needs better wave function. The expectation value of the Hamiltonian (E) for any wave function, Ψ, is an upper bound to the exact ground state energy, . The variational energy is defined as, ……..(5)

Therefore, a variational procedure is used to minimizing the energy and to obtain best wave function from the trial wave function.

The ground state energy may be found by searching all possible wavefunctions for the one that minimizes the total energy. Hartree-Fock theory consists the structure of ψ and it is assumed to be an antisymmetric product of functions (fi) each of which depends on the coordinates of a single electron, that is; where det indicates a Slater determinant.11,12 Substitution of ψ into the Schrödinger equation results in an expression for the Hartree Fock