THE ELECTRON-DENSITY DISTRIBUTION IN ALPHA-TIN FROM POWDER X-RAY DATA BY THE MAXIMUM-ENTROPY METHOD

The electron density distribution map of alpha-tin has been drawn by the maximum-entropy method (MEM) with 11 independent and two combined structure factors, which were determined by the powder pattern decomposition from x-ray data. The final R and R(u), factors were 0.80% and 0.89%, respectively, though a small amount of beta-tin was contained in the specimen. The obtained map indicates that the bonding electrons are clearly seen between the two adjacent tin atoms in the (110) plane with the 0.6 e Angstrom(-3) level. This value was about twice that of germanium. The structure factor F(222)e(-M) for the 222 forbidden reflections at 293 K calculated from the MEM density is +0.4350. The results are discussed by comparing with the electron density maps of C (diamond), Si and Ge.