On the basis of density functional theory, we have investigated the intraatomic energy, electronegativity and hardness of an atom in a molecule and introduced the adjusting factor k for interatomic interactive energy terms in the total molecular energy expression. This allows not only to explain and treat more reasonably some problems but also increase greatly the computed precision and the applied areas. On these grounds, we have developed a new scheme of direct calculation of total molecular energy and applied it to calculations of about 100 molecules or groups of different sizes, The results obtained are in good agreement with those from ab initio calculations at the same level, The relative deviation of the two results is less than one thousandth. In addition, the new method presented here is advantage of simplicity, rapidness and easy perform as well. So that it provides an efficent and practical method for the energy calculations of macromolecular system.

Key words: ELECTRONEGATIVITY