High resolution electron density mapping for LiF and NaF by maximum entropy method (MEM)

High resolution maximum entropy method (MEM) electron density maps have been elucidated for LiF and NaF using reported X-ray structure factors. The ionic nature of the bonding between constituent atoms in both the systems is found to be well pronounced and clearly seen from the electron density maps. The resolution of the present MEM maps is 0.063 Angstrom per pixel for LiF and 0.072 Angstrom per pixel for NaF along the three crystallographic axes. The electron density at the middle of the bond along [111] is found to be 0.0673 e/Angstrom(3) for LiF and 0.003 e/Angstrom(3) for NaF showing the different ionic strengths of the bonding. The electron density along [100] and [110] has also been drawn and analyzed. The inequality in the ionicity for the individual atoms and the electron content for different ionic radii have also been analyzed and compared with already published results. The wR(MEM) obtained from MEM analysis is 0.3% for LiF and 0.79% for NaF. (C) 2002 Elsevier Science Ltd. All rights reserved.