A NEW SCHEME FOR DETERMINATION OF ATOMIC CHARGES AND BOND CHARGES IN LARGE MOLECULES

On the basis of density functional theory and electronegativity equali zation principle, a new scheme has been developed for determination of atomic charges and bond charges in large molecules, In the new scheme , the molecular electron density rho(mol)((r) over right arrow) is par titioned as rho(mol)((r) over right arrow) = Sigma/alpha rho alpha((r) over right arrow) + Sigma/alpha-beta rho alpha-beta((r) over right ar row), where rho alpha((r) over right arrow) and rho alpha-beta((r) ove r right arrow) are the the electron densities located on the atom ct a nd bond alpha-beta, respectively, The parameters A, B, C and D are the valence-state electronegativity and valence-state hardness, They are obtained by calibrating through model molecule calculations and are tr ansferable and consistently usable for calculating the charge distribu tions in large molecules, The new scheme is tested through determinati on of atomic charges and bond charges in several large molecules. It h as been shown that the results of atomic charges and bond charges obta ined by the new scheme dovetail those obtained by ab initio method ver y well, In addition, the new scheme presented here has the advantage o f simplicity, rapidness and easy perform as well, so that it provides an efficient and practical method for calculation of the charge distri bution for a macromolecular system.