Introduction to Crystal Lattice
Solids are divided into two types.
An amorphous solid has no defined shape or structure.
Another is a crystalline structure, or crystals, which have a well-organized particle structure.
A regular arrangement of atoms makes up the structure of crystals (or particles). A crystal lattice is a three-dimensional representation of a certain arrangement of atoms.
As a result, a lattice is a set of points arranged in a specific order that describes the arrangement of particles in a crystalline solid.
Auguste Bravais, a French scientist, discovered that there are fourteen different three-dimensional lattices to choose from.
These 14 arrangements of Bravais Lattice have six basic shapes and have some important characteristics:
A lattice point is a spot on the lattice that represents one crystal particle.
An atom, a molecule, or even ions could be this particle.
A crystal's lattice points are linked together by straight lines.
The geometry (or shape) of the crystal is obtained by combining these points.
Each of the fourteen lattices has a different geometry.
Introduction to Unit Cell
The most basic and least volume-consuming repeating structure of any solid material is the unit cell.
Its objective is to simplify crystalline patterns formed by solids.
The repeated arrangement of unit cells makes up the complete space lattice. Even by itself, a unit cell is a geometric shape.
There are three edges to it. These three edges also form three different angles. A unit cell's edges are as follows:
A: edges defined by b and c lattice vectors
B: edges defined by a and c lattice vectors
C: edges defined by a and b lattice vectors
The unit cell's interfacial angles are as follows:
α: the angle formed by the edges b and c
β: angle between a and c edges
γ: angle between a and b edges
Cells of the Primitive Unit
Atoms, molecules, or ions are only found at the corners of a primitive unit cell's lattice.
At a basic unit cell, there are no particles in any other position. As a result, a primitive unit cell only has one lattice point.
Unit Cells That Aren't Primitive
There are particles in this form of unit cell not just at the corners of the lattice, but also in other locations.
These additional constituent particles can be found on the unit cell's surface or inside it.
In a non-primitive unit cell, there are several lattice points. There are three different types of non-primitive unit cells:
Body-Centered: It has a single particle in the middle of the body. Other particles (one or more) are located at the lattice's corner.
Face Centered: This has particles on all of the lattice's faces, as well as particles on the corners.
End Centered: The opposite faces have particles at the corners and one particle in the center.
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FAQs on Crystal Lattices and Unit Cell
1. What are Lattice Defects?
In theory, the ionic lattice only shows the representation of a solid crystal, where the atoms or ions get repeated at regular intervals (also known as unit cells). However, in reality, crystals often exhibit lattice defects, where an atom or many atoms can be missing from its estimated position into particular sites. Such crystals could be examples of lattice defects that can lead to having better conducting abilities in compounds. Some of the more popular defects are Frenkel defect, Schottky defects, etc.
2. Give the Significance of a Lattice Point.
The following are the significance of a lattice point:
Also known as the lattice side, each point in a crystal lattice represents a constituent particle known as an atom, molecule, or an ion.
Each lattice point comes from a similar surrounding, except those present on the surface or corner of a crystal.
When a line is drawn between two lattice points, it would have to pass multiple identical locations at regular intervals.
When joined on straight lines, the lattice points can bring out the lattice geometry, which does not show any chemical bondings.
