MADELUNG FIELD AND ELECTRON CORRELATION IN PHYSISORPTION

The effect of the Madelung field corresponding to formal point charges +/-e arranged according to the fcc lattice of LiF upon CO, N2 and NO molecules is studied in order to isolate the purely electrostatic interaction from the other forces acting in the related physisorption processes. The polarization which is produced in those molecules by the Madelung field is analyzed in terms of dipole and quadrupole moments, as well as in terms of electron charge distributions. The influence of the electron correlation is taken into account by using the QCISD technique, which requires the semi-infinite lattice being simulated with a suitable cluster of point charges.