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Questions and Answers
The nucleus attracts further atoms to form new lattice planes.
The nucleus attracts further atoms to form new lattice planes.
True
Atoms take up positions randomly around the nucleus.
Atoms take up positions randomly around the nucleus.
False
Lattice planes are formed without the influence of a nucleus.
Lattice planes are formed without the influence of a nucleus.
False
The arrangement of atoms around the nucleus is three-dimensional.
The arrangement of atoms around the nucleus is three-dimensional.
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Lattice planes cannot be formed by further atoms.
Lattice planes cannot be formed by further atoms.
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A disturbance can lead to a polycrystalline result.
A disturbance can lead to a polycrystalline result.
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Crystalline materials have a random arrangement of atoms.
Crystalline materials have a random arrangement of atoms.
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Non-crystalline materials are also known as amorphous materials.
Non-crystalline materials are also known as amorphous materials.
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Polycrystalline materials have a periodic atomic arrangement.
Polycrystalline materials have a periodic atomic arrangement.
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The arrangement of atoms in a non-crystalline material is defined and repetitive.
The arrangement of atoms in a non-crystalline material is defined and repetitive.
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In morphology, the words 'form' and 'habit' refer only to the internal structure of a crystal.
In morphology, the words 'form' and 'habit' refer only to the internal structure of a crystal.
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The faces of a crystal are parallel to lattice planes occupied by atoms.
The faces of a crystal are parallel to lattice planes occupied by atoms.
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Edges of a crystal are perpendicular to lattice lines occupied by atoms.
Edges of a crystal are perpendicular to lattice lines occupied by atoms.
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Morphology and crystal structure refer to the same aspect of crystals.
Morphology and crystal structure refer to the same aspect of crystals.
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Lattice planes in a crystal can influence its external morphology.
Lattice planes in a crystal can influence its external morphology.
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The equation $ruv= ua + vb$ describes the repetition of a point along a 2D plane.
The equation $ruv= ua + vb$ describes the repetition of a point along a 2D plane.
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A space lattice is defined as a two-dimensional array of points.
A space lattice is defined as a two-dimensional array of points.
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In a face centered lattice, atoms are located only at the corners of the unit cell.
In a face centered lattice, atoms are located only at the corners of the unit cell.
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In the equation $ruv= ua + vb$, both u and v can take non-integer values.
In the equation $ruv= ua + vb$, both u and v can take non-integer values.
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Corner centered lattices contain atoms at the corners and the middles of the sides.
Corner centered lattices contain atoms at the corners and the middles of the sides.
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Each point in a space lattice has unique surroundings.
Each point in a space lattice has unique surroundings.
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There are 14 Bravais lattices that represent the ways to fill space in three dimensions.
There are 14 Bravais lattices that represent the ways to fill space in three dimensions.
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The concept of repeating points applies to both 2D and 3D spaces.
The concept of repeating points applies to both 2D and 3D spaces.
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Only face centered lattices can fill three-dimensional space.
Only face centered lattices can fill three-dimensional space.
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Atoms in a corner centered lattice are only found at the corners of the unit cell.
Atoms in a corner centered lattice are only found at the corners of the unit cell.
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There are 32 unique ways in which lattice points can be arranged in space.
There are 32 unique ways in which lattice points can be arranged in space.
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Symmetry operations only generate linear arrangements of lattice points.
Symmetry operations only generate linear arrangements of lattice points.
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Point-groups refer to non-translation elements in lattice arrangements.
Point-groups refer to non-translation elements in lattice arrangements.
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Point groups can occur in two-dimensional arrangements only.
Point groups can occur in two-dimensional arrangements only.
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Lattice points are arranged solely based on their translational symmetry.
Lattice points are arranged solely based on their translational symmetry.
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Study Notes
Introduction to Crystallography
- Matter exists in three states: gas, liquid, and crystal.
- Gases have no fixed volume or shape, their molecules move rapidly with weak attractive forces and high kinetic energy.
- Liquids have a constant volume but adopt the shape of their container. Molecules are in contact but not fixed, with attractive forces moderating kinetic energy as temperatures decrease.
- Crystals have a fixed shape and volume, independent of their container. They form a three-dimensional framework of attractive interactions with molecules in a fixed, regular order.
Crystallization/Crystallization
- Crystallization is the process in which a solid forms, organizing atoms/molecules into an ordered structure (crystal).
- Crystallization occurs through various methods, like precipitation from solutions, freezing, and sometimes deposition from a gas.
- Crystals are solid substances with specific crystal arrangements and fixed chemical structures.
Crystal Growth
- Crystals form in two steps:
- Nucleation: Small clusters of atoms come together to form a nucleus (initial crystal structure with a repeating pattern).
- Growth: The nucleus attracts more atoms, adding layers in accordance with the crystal's structure. Slow growth creates dominant faces.
- Crystal growth rates depend on temperature, pressure, and solution saturation.
- Single crystals grow from a single nucleus, while crystal aggregates develop simultaneously from multiple nuclei. This leads to polycrystalline structures with disordered grain boundaries.
Atomic Arrangement
- Crystalline solids exhibit a periodic arrangement of atoms.
- Non-crystalline (amorphous) solids have a disordered arrangement of atoms.
- The periodicity of atoms in crystalline solids is described using a network of points in space called the lattice.
The Crystalline State
- Crystals display diverse appearances, but have some common characteristics.
- Many crystals have smooth faces exhibiting regular shapes, and these shapes vary considerably.
- Crystal fragments often have similar shapes (cleavage).
- Crystals exhibit different colors in different directions (pleochroism) due to optical absorption.
- Crystal hardness varies significantly.
Fundamentals of Morphology
- Morphology studies a crystal's outer form/habit (face shapes, sizes, and edges).
- The crystal's form is defined by its faces.
- Habit describes the relative sizes of faces, including equant (similar sizes), planar (flat), tabular (table-like), prismatic (prism-like), and acicular (needle-like).
Crystal Structure
- A crystal lattice is an array of points in space, each with identical surrounding points. The unit cell is the smallest repeating unit.
- Lattice points in crystals are occupied by atoms, ions, or molecules.
- The identical arrangement of unit cells forms the crystal structure.
- Lattice translations repeat the arrangement of atoms throughout the crystal.
The Unit Cell
- The unit cell is the smallest repetitive unit in a crystal lattice.
- There are three basic types: primitive, body-centered, and face-centered.
The Lattice and Its Properties
- A lattice is a three-dimensional array of points in space, where all points have identical environments.
- Defining points of a lattice produces line, plane, and space lattices.
- The periodicity of points along a line is described with vectors, that are also used to define planes and space lattices.
- Crystallographic axes are employed to develop a system for describing a crystal lattice in 3 dimensions
Classification of Lattices
- There are 7 crystal systems and 14 Bravais lattices.
- The 7 crystal systems are based on differences in the angles and lengths of the unit cell axes.
- Crystals are described according to the shapes and angles of their repetitive cells.
- Bravais lattices are fundamental arrangements of atoms in each system that reflect the symmetry and pattern of the repeating unit cell.
Crystal Systems
- Different crystal systems are defined by the angles and lengths of their unit cell.
- Different crystal systems have unique possible types of unit cells (Bravais patterns).
Point and Space Groups
- Point groups describe symmetry in crystals but don't account for translations (shifts).
- The actual arrangement of atoms in a unit cell is described by Space Groups
- A large number of 3d shapes are generated by point groups and translation actions.
Point Coordinates
- Each point within a unit cell can be described by its coordinates using the unit cell vectors(a, b, and c).
- Coordinates are expressed in fractions of the unit cell parameter (a, b, and c) lengths.
Crystal Directions
- Crystallographic directions are defined using integers (u, v, w) that describe the ratio of the intercepts with the axes of the unit cell.
- Equivalent vectors have the same direction indices.
- Directions are given in < > notation.
Crystal Planes
- Crystallographic planes have indices that combine smallest integral values for intercepts with the axes of the unit cell.
- The Miller indices (h,k,l) are reciprocals of intercepts, in terms of unit cell dimensions a/h, b/k, c/l.
- Multiple planes with the same indices form a family of planes in<{} brackets>.
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Description
Explore the fascinating world of crystallography, where matter exists in various states, including crystals. This quiz covers the definition and properties of gases, liquids, and solids, along with the crystallization process and methods of crystal growth. Test your knowledge of how these structures form and their significance in science.
