ELECTROSTATIC PROPERTIES IN ZEOLITE-TYPE MATERIALS FROM HIGH-RESOLUTION X-RAY-DIFFRACTION - THE CASE OF NATROLITE

High-resolution x-ray-diffraction data of natrolite at room temperatur e give by multipolar refinement an analytical expression of the electr on density which permits the calculation of net atomic charges and ele ctrostatic potential. The observed net charges show that the structura l formula of natrolite may be written Na2Al2Si2O8(SiO2),2H(2)O. The el ectrostatic energy of one sodium ion inside the crystal is estimated t o -21.6 eV. Calculation of the electrostatic potential excluding one s odium shows that the minimum is precisely at the removed Na position.