Computers ab initio calculations

Economy of computation ab initio calculations of the electronic energy for larger molecules would have been many orders of magnitude more expensive. 

What takes place in an ab initio calculation is pretty complicated. However, because all the mathematics is done by a computer, ab initio calculations are not difficult to perform. So, let s briefly review what is done in ab initio methods. This approach is generally called the Roothaan procedure, or Roothaan s formulation of the Hartree-Fock method (minus step 7, below). 

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