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

The electron density distribution map of alpha-tin has been drawn by t he maximum-entropy method (MEM) with 11 independent and two combined s tructure factors, which were determined by the powder pattern decompos ition 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 ar e clearly seen between the two adjacent tin atoms in the (110) plane w ith the 0.6 e Angstrom(-3) level. This value was about twice that of g ermanium. The structure factor F(222)e(-M) for the 222 forbidden refle ctions at 293 K calculated from the MEM density is +0.4350. The result s are discussed by comparing with the electron density maps of C (diam ond), Si and Ge.