correlation energy within Hartree Fock formalism

to achieve post Hartree Fock accuracy.

technique and perturbation methodology we can

construct a weave equation which on projection

gives very simple equation for correlation

energy. Correlation energy only depends on the

amount of perturbation. This method is applied

for few small molecules. It is found that this

method produces very accurate results which is

comparable to CCSD method.

termed as Extended Hartree Fock (EHF)

method is proved to be a very good tool for

electronic structure theory as its computational

requirement is equivalent to HF method but its

accuracy is comparable to Coupled Cluster

based methods.