Chemical bonds from the condition of minimal pair fluctuation: Correlated case

A novel approach connecting the intuitive idea of chemical bond with a quan tum mechanical description is developed. Starting from a previous analysis based on SCF pair densities, a study of the electron-pair fluctuation is pe rformed. The method requires the knowledge of the correlated pair density, and the minimization of bond fluctuations was done through a Jacobi element ary rotation scheme. A parallelism between pair fluctuation and bond breaki ng is found when fluctuations over the bond distance are studied. An abrupt change of fluctuation around a critical value of distance is found, preclu ding the possible association of bond breaking with a sharp rather than a s mooth process. The results also confirm the importance of the electron-pair ing Lewis model. (C) 1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 85-9 1, 1999.