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Ch.12 - Solids and Modern Materials
Chapter 12, Problem 30a

The unit cell of a compound containing potassium, aluminum, and fluorine is shown here. (a) What type of lattice does this crystal possess (all three lattice vectors are mutually perpendicular)?
Diagram of a simple cubic unit cell with dimensions and angles labeled.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Crystal Lattice

A crystal lattice is a three-dimensional arrangement of atoms or molecules in a crystalline material. It is defined by its unit cell, which is the smallest repeating unit that reflects the symmetry and structure of the entire crystal. The arrangement of these unit cells determines the properties of the material, including its symmetry, density, and how it interacts with light.
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Unit Cell Parameters

Unit cell parameters include the lengths of the edges (a, b, c) and the angles between them (α, β, γ) that define the geometry of the unit cell. These parameters are crucial for identifying the type of crystal system, such as cubic, tetragonal, or orthorhombic. In the given question, the specific values and angles help determine the lattice type of the compound.
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Types of Crystal Lattices

Crystal lattices can be classified into several types based on their geometric arrangement. Common types include simple cubic, body-centered cubic, and face-centered cubic, each characterized by specific arrangements of atoms and angles. The question indicates that all three lattice vectors are mutually perpendicular, suggesting a cubic or orthogonal lattice structure, which is essential for determining the type of lattice present in the compound.
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