Shift energy scene

The next set of open-shell cluster expansion theories to appear on the scene emphasized the size-extensivity feature (al), and all of them were designed to compute energy differences with a fixed number of valence electrons. Several related theories may be described here - (i) the level-shift function approach in a time-dependent CC framework by Monkhorst/56/ and later generalizations by Dalgaard and Monkhorst/57/, also by Takahasi and Paldus/105/, (ii) the CC-based linear response theory by Mukherjee and Mukherjee/58/, and generalized later by Ghosh et a 1/59.60.107/,(iii)the closely related formulations by Nakatsuji/50,52/ and Emrich/62/ and (iv) variational theories by Paldus e t a I / 54/ and Saute et. al /55/ and by Nakatsuji/50/. 

Engineering is based on fundamentals and the dynamic balance among economic, operability, sustainability, safety, environmental, legal, ethical, and time constraints. It is dynamic, because the development of new technology, catalysts, and materials of construction, and the shifting economical, social, and political scenes, mean that the processes we develop, improve, and operate in the future will be dramatically different from past practice. We say it is based on fundamentals, because mass, energy, momentum, and charge will still be conserved. 

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