Question

1. Sketch the unit cell and calculate the density of BeO in gm/cm'. It has the zinc blende structure. What is the Coordination Number for the Beations What is the Coordination Number for the 02 ions 2. Sketch the unit cell and calculate the density of Si in gm/cm°. It has the diamond cubic structure What is the Coordination Number for the Si atoms?

Answer 1

Dear Student, Kindly refer to the complete solution of your first question. Feel free to ask if you face difficulty in understanding any step of the solution attached, so that we can assist you in a better way.

Dear student, Structure of Zinc blende beo :- is The eo arrangement as possessed by Bee called cubic close packing feep th which o2-ious are present at the corners as well as at the center of each face of the cube Beations ale plesent in alternate teteahedral . . قهوه fach beat is surrounded tetrahedrally by towe o2-ion and each o²-ious is surrounded tetrahedrally by fowe Be at ions. Thus I coordination no. fol Be 2+ fors = 4 Coordination no. for od-ion = 4 In an fcc unit cell, there all 8 Tetia- hedral woods. Thus, there all 4 Beations and 4 02-ions giveng 4 Be o per unit cell. unit cell Representation : - 2.g²-ions O: Be 2+ ions P.T-O

Boo has zinc blende crystal structules there all 4 Be 2+ ions and 4 o ione per unit cell. a= 4 (air) BY Jonic radii Be 27 = 0.034 nm - 02- = 0.132 nm Q=4_10.034 +0.13) a = 0.383nm manitou ( 4 Bet9.012 g/molt (402-X16.00 g/mol) 6.022416 iows/mal 21-66 x lodd The density m m 1.66 x 1080g (3-83x108 Em] 3 = 2.95g/cm²