Primary Properties and their Derivatives

In their classic paper Mathematical Problems in the Complete Quantum Predictions of Chemical Phenomena , Boys and Cook (1960) divided the determination of an ab initio electronic wavefunction into distinct logical stages which include the 

This paper represented advanced thinking in 1960, and whilst we might now be interested to add extra steps such as 

Boys and Cook refer to these properties as primary properties because their electronic contributions can be obtained directly from the electronic wavefunction As a matter of interest, they also classified the electronic energy as a primary property. It can t be calculated as the expectation value of a sum of true one-electron operators, but the Hartree-Fock operator is sometimes written as a sum of pseudo one-electron operators, which include the average effects of the other electrons. 

Thirdly, induced properties are those that measure the response of a system to an applied field. I will concentrate on polarizabilities (for which the external field is electric) and magnetizabilities (for which the apphed field is magnetic) in a later chapter. 

Finally, Boys and Cook refer to interactions between systems as the fourth category of molecular property. 

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