a) C 60 fullerenes crystallizes into an fcc lattice, also known as fullerite, wi

Question

a) C60 fullerenes crystallizes into an fcc lattice, also known as fullerite, with a lattice constant of a=14.17 Å. The diameter of a C60 molecule is about 0.71 nm. Calculate the density of fullerite

b) Metal ions can be inserted into the octahedral sites of fullerite structure. What is the maximum ionic radius that can be accommodated without distorting the C60 lattice?

c) C-C bonds in fullerenes are described as sp2 -sp3 admixtures. Which do you expect to possess more sp3 character, C-C bonds in C60 fullerenes or C120 fullerenes? Briefly explain why

Explanation / Answer

a) denisty for FCC = 4 X Mass in unit cell/volume of unit cell

                            = (4 x 60 x 12)/ NA (14.17x10-8)3

                            = 1.68 g/cc

NA = avogardro no = 6.023 x1023

Volume of unit cell = a3

b) FCC conatins both octahedral and tertrahedtal voids.

To have octahedral we voids we can get maximum size of Metal that can be acommodated.

The Radius of Vacancy = 0.414 x Radius of Unit cell atom

                                   = 0.414 x (0.71/2) = 0.14697 nm

c) C60 has greater SP3 Character, than C120

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