SEMIEMPIRICAL QUANTUM-CHEMICAL CALCULATION OF ELECTROSTATIC POTENTIALGENERATED BY IDEALIZED LAYER OF TALC

The electrostatic potential of an isolated layer of talc Mg3Si4O10(OH) 2 in idealized structure (layer group symmetry p6mm) was computed usin g the electron distribution obtained from semiempirical INDO/2 calcula tion. Cluster of 9348 atoms generated by translational multiplication of identical replicas of a basic motive was used as a model of the two -dimensional infinite layer. The basic motive was selected from the in nermost part of the 298 atom layer on which the electronic structure c alculations were performed. The model cluster was chosen so as to pres erve the symmetry of the whole system, and to include all the non-negl igible contributions of the entire layer to the electrostatic potentia l in the chosen region, with a sufficient accuracy. The knowledge of t he electrostatic potential enables to obtain harmonic frequencies of v ibration of a proton hypothetically adsorbed in vacuo on the surface o f the ideal layer of talc.