Simulation Methods Applied to Carbon Reactions

2 MOLECULAR SIMULATION METHODS APPLIED TO CARBON REACTIONS 

1 Electronic Structure Methods (or Quantum Mechanics Methods) 

Electronic structure methods or quantum mechanics (QM) methods use the laws of quantum mechanics rather than classical physics as the basis for their computations. QM states that the energy and related properties of a molecule may be obtained by solving the Schrddinger equation H- r = Eiji. For any but the smallest systems, however, exact solutions to the Schrddinger equation are not computationally practical. QM methods are characterized by various mathematical approximations to its solution. There are three classes of QM methods semiempirical, ab initio, and density functional theory (DFT). 

Semiempirical Methods Semiempirical methods use parameters derived from experimental data to simplify the computation. They solve an approximate form of the Schrddinger equation that depends on having appropriate parameters available for the type of chemical system under investigation. Different semiempirical methods are characterized largely by their differing parameter sets. 

HMO (Hiickel molecular orbital theory) is the simplest quantitative molecular orbital theory. It was developed in the 1930s by Erich Hiickel to describe planar hydrocarbons with conjugated jt bonds [13]. HMO is based on the idea of o — jt separation, treating rr electrons only. HMO calculations are the only ones that are practical to do without the aid of a computer, giving rather poor energies and orbital functions but faithfully reproducing the symmetry properties of orbitals. 

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