Dynamical Electron Correlation Within Hartree-Fock Limitation

Aim: Calculation of dynamical electroncorrelation energy within Hartree Fock formalismto achieve post Hartree Fock accuracy. Achievement: Using intermediate Hamiltoniantechnique and perturbation methodology we canconstruct a weave equation which on projectiongives very simple equation for correlationenergy. Correlation energy only depends on theamount of perturbation. This method is appliedfor few small molecules. It is found that thismethod produces very accurate results which iscomparable to CCSD method. Conclusion: The present method which istermed as Extended Hartree Fock (EHF)method is proved to be a very good tool forelectronic structure theory as its computationalrequirement is equivalent to HF method but itsaccuracy is comparable to Coupled Clusterbased methods.