GeologyLesson 1 of 1 in the course Minerals

Crystal Structures: Lattices, Miller Indices, Defects, and Properties

5 flashcards · 5 quiz questions · 5 match pairs · 3 fill-in sentences · English

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Summary

A crystal is not simply a collection of particles: its atoms, ions, or molecules are arranged in an orderly pattern that repeats through space. This lesson introduces the unit cell, lattice parameters, particle coordinates, and the role of symmetry.

Crystal structure describes the ordered arrangement of atoms, ions, or molecules in a crystalline material. The repeating order extends in three dimensions. A helpful analogy is a tiled floor: one tile pattern is repeated by translations to build a much larger surface.

All flashcards

What is a crystal structure?
The ordered arrangement of atoms, ions, or molecules that repeats in three-dimensional space.
What is a crystallographic asymmetric unit?
The smallest region needed to specify a crystal structure; symmetry operations generate the equivalent positions.
What is a basis in crystallography?
The group of particles associated with each point of a Bravais lattice.
What is polymorphism?
The existence of multiple crystalline forms of the same material.
What does coordination number measure?
The number of nearest neighbors surrounding a central atom.

Quiz questions

  1. In Miller indices, what does a zero index indicate about a crystal plane?Answer: The plane is parallel to the corresponding axis.
  2. In a cubic crystal, how is plane (hkl) oriented relative to direction [hkl]?Answer: The direction is normal to the plane.
  3. Which sequence describes cubic close packing?Answer: ABCABC
  4. How many distinct Bravais lattices occur in three dimensions?Answer: 14
  5. What symmetry property is required for a crystal class to be piezoelectric?Answer: It lacks inversion symmetry.

Based on the Wikipedia article Crystal structure, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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