The resistivity (a measure of electrical resistance) of...

The resistivity (a measure of electrical resistance) of graphite is $(0.4$ to $5.0) \times 10^{-4} \mathrm{ohm} \cdot \mathrm{cm}$ in the basal plane. (The basal plane is the plane of the six-membered rings of carbon atoms.) The resistivity is $0.2$ to $1.0 \mathrm{ohm} \cdot \mathrm{cm}$ along the axis perpendicular to the plane. The resistivity of diamond is $10^{14}$ to $10^{16} \mathrm{ohm} \cdot \mathrm{cm}$ and is independent of direction. How can you account for this behavior in terms of the structures of graphite and diamond?

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Key Concepts

Crystal Structure and Hybridization

The crystal structures of graphite and diamond are fundamentally different due to their respective hybridizations. Graphite is composed of layers of sp2-hybridized carbon atoms arranged in a hexagonal lattice, which allows for delocalized pi electrons within the basal plane, contributing to conductivity. In contrast, diamond consists of sp3-hybridized carbon atoms arranged in a strong covalent tetrahedral network, which leads to its insulating behavior as all electrons are localized in sigma bonds.

Anisotropy

Anisotropy refers to the directional dependence of a material's properties. In graphite, because of its layered structure, electrical conductivity is much higher within the layers (the basal plane) where electrons can move freely, while conductivity is significantly lower perpendicular to the layers where there is no delocalized electron pathway. Diamond, having a uniform tetrahedral structure, exhibits isotropic behavior, with its properties being similar in all directions.

Resistivity

Resistivity is a measure of how strongly a material opposes the flow of electric current. It provides insight into the ease or difficulty with which electrons can move through a material when an electric field is applied, which is directly influenced by the material's internal structure and bonding.

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