Crystals and Their Properties Quiz

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Questions and Answers

What characteristic defines crystals?

  • Atoms are arranged in a long-range order. (correct)
  • They have no definite shape.
  • Particles are arranged randomly.
  • They consist of only one type of atom.

Which of the following is an example of a crystalline substance?

  • Rubber
  • Plastic
  • Glass
  • Sodium chloride (correct)

What term is used to describe materials that have randomly arranged particles?

  • Amorphous (correct)
  • Cubic
  • Polymeric
  • Crystalline

In contrast to crystals, which statement is true for amorphous materials?

<p>They lack a long-range order in their atomic structure. (C)</p> Signup and view all the answers

Which of the following is NOT true about crystalline substances?

<p>They can be formed from metals only. (C)</p> Signup and view all the answers

What is the resulting structure when atoms are replaced by geometric points in their stable positions?

<p>A geometric structure representing the crystal's properties (A)</p> Signup and view all the answers

What property does the geometric structure of points possess when atoms are replaced by these points?

<p>Geometric properties of the crystal (C)</p> Signup and view all the answers

In what position are the geometric points located when atoms are replaced?

<p>In the stable position of the atoms (B)</p> Signup and view all the answers

What transformation occurs to the atoms when creating the geometric structure?

<p>Atoms are replaced by points representing their positions (D)</p> Signup and view all the answers

Which of the following statements best describes the outcome of replacing atoms with geometric points?

<p>A geometric representation that maintains the crystal's properties is formed. (D)</p> Signup and view all the answers

What are the four basic types of Bravais lattices in three dimensions?

<p>Primitive lattice, Body center lattice, Face center lattice, Base or side center lattice (D)</p> Signup and view all the answers

Which lattice is not one of the basic types of Bravais lattices?

<p>Rectangular centered (C)</p> Signup and view all the answers

How many crystal systems are the five types of basic lattices distributed over?

<p>Seven (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of a primitive lattice?

<p>Always has a higher density than other lattices (C)</p> Signup and view all the answers

Which of the following statements about the Bravais lattices is incorrect?

<p>Hexagonal lattice is one of the basic Bravais lattices. (B)</p> Signup and view all the answers

What is the relationship between the nearest neighbor distance d and the atomic radius r in the context of a face-centered cubic lattice?

<p>r = 1/2d (D)</p> Signup and view all the answers

Which of the following is NOT a primitive vector of a face-centered cubic (FCC) structure?

<p>a/2(k+i) (B)</p> Signup and view all the answers

What is the calculated volume of the primitive cell of a face-centered cubic (FCC) lattice?

<p>(1/4)a³ (D)</p> Signup and view all the answers

What does the filling factor or packing factor measure in a crystalline structure?

<p>The ratio of the volume occupied by atoms to the total volume (B)</p> Signup and view all the answers

How is the volume of the unit cell calculated using the primitive vectors in a cubic system?

<p>Volume = |a.b xc| (C)</p> Signup and view all the answers

What does the notation <110> represent in crystallography?

<p>All directions of equivalent type in a crystal (A)</p> Signup and view all the answers

What does the term 'band axis' refer to in crystal directions?

<p>A direction along which a group of intersecting surfaces aligns (C)</p> Signup and view all the answers

Which statement accurately describes intersecting surfaces in crystals?

<p>They share a common direction or domain axis. (D)</p> Signup and view all the answers

In crystallography, which of the following options represents a possible equivalent direction to <110>?

<p>[101] (B)</p> Signup and view all the answers

In the context of crystallography, what is meant by 'domain axis'?

<p>A common direction along which surfaces intersect (A)</p> Signup and view all the answers

What are the steps to find the Miller indices for a surface intersecting the axes at x=3, y=6, z=2?

<p>Inverse the coordinates, multiply by the least common multiple, then state the indices. (D)</p> Signup and view all the answers

Given the intersection x=4, y=∞, z=1/2, what are the resulting Miller indices?

<p>(108) (A)</p> Signup and view all the answers

What is the correct method for determining the Miller coefficients for the intersection at x=4, y=∞, z=-1/6?

<p>Inverse the coordinates, multiply by 4. (C)</p> Signup and view all the answers

Which of the following sets of axes corresponds to the Miller indices (213)?

<p>x=3, y=6, z=2 (B)</p> Signup and view all the answers

What is the primary purpose of forming a plane from the Miller coefficients when determining crystal direction?

<p>To create a visual representation of the crystal structure. (A)</p> Signup and view all the answers

Flashcards

Square lattice

A type of crystal lattice where the unit cells are arranged in a square pattern.

Hexagonal lattice

A type of crystal lattice where the unit cells are arranged in a hexagonal pattern.

Primitive lattice

A type of crystal lattice where the unit cell has one lattice point at each corner.

Body center lattice

A type of crystal lattice where the unit cell has one lattice point at each corner and one lattice point at the center of the cell.

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Face center lattice

A type of crystal lattice where the unit cell has one lattice point at each corner and one lattice point at the center of each face.

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Crystal Structure Representation

In crystallography, replacing atoms with geometric points at their stable positions creates a geometric structure representing the crystal's properties.

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Long-range order

The repeating pattern of atoms in a material extends over a large distance.

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Geometric Structure of Points

A geometric structure formed by representing each atom in a crystal with a point placed at its stable position.

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Crystalline

Materials with long-range order, meaning atoms are arranged in a repeating pattern.

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Stable Position of an Atom

The stable configuration of an atom within a crystal lattice.

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Amorphous

Materials with short-range order; their atoms lack a repeating pattern.

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Geometric Properties of Crystals

The geometric properties of a crystal, such as its shape, symmetry, and unit cell, are maintained in its geometric structure of points.

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Sodium chloride (salt)

A common example of a crystalline material with a regular, repeating arrangement of sodium and chlorine atoms.

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Factors Determining Stable Positions

The stable position of each atom in a crystal lattice is determined by factors such as interatomic forces and electrostatic interactions.

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Diamond

A very hard, crystalline material composed of carbon atoms arranged in a tetrahedral structure.

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Nearest Neighbor Distance in FCC

The distance between two nearest atoms in a face-centered cubic (FCC) lattice is half the length of the face diagonal.

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Radius-Lattice Constant Relationship in FCC

The relationship between the radius (r) of an atom and the lattice constant (a) in an FCC lattice is given by √2a = 4r, where a is the length of the edge of the unit cell.

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Primitive Cell Volume in FCC

The volume of the primitive cell of a face-centered cubic (FCC) lattice is 1/4 the volume of the conventional unit cell.

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Filling Factor

The filling factor (or packing factor) is the ratio of the volume occupied by atoms to the total volume of the unit cell.

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Primitive Vectors of FCC

The vectors that define the edges of the primitive unit cell in a face-centered cubic (FCC) lattice are a/2(i+j), a/2(j+k), and a/2(i+k), where a is the lattice constant.

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What are Miller Indices?

The Miller indices represent a set of three numbers that define the orientation of a crystal plane.

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How are Miller Indices calculated?

To find the Miller indices of a crystal surface, take the inverse of the coordinates of the intersection with the axes, multiply by the least common multiple, and simplify to the smallest possible integers.

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Miller Indices for Infinite Intersections

When a crystal surface intersects an axis at infinity, the Miller index for that axis is zero.

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Why are Miller Indices important?

The Miller indices help us understand the geometry of a crystal and predict properties like cleavage and growth patterns.

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What does a negative sign in a Miller index mean?

A negative sign in a Miller index indicates that the plane cuts the corresponding axis on the negative side of the origin.

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Band Axis

The direction of a crystal, representing a common direction along which a group of intersecting surfaces share. This signifies that these surfaces belong to the same domain.

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Domain

A group of surfaces sharing a common direction or band axis. They are considered part of the same domain within a crystal.

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Direction Notation

A notation used to represent directions in crystals. It uses angle brackets and three numbers, like this: . Each number represents the direction along a specific crystallographic axis. For example, <110> means all directions equivalent to [101], [101], [011], etc.

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Crystallographic Axes

Crystallographic axes are imaginary lines used as references within a crystal structure. They define the orientation of a crystal lattice and help describe directions and planes within the crystal.

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Equivalent Directions

The formula represents directions within a crystal structure. It effectively describes a set of equivalent directions because crystals are often symmetrical. So, <110> includes all directions that are equivalent to [101],[101],[011],[011],[110],[101],[011], etc.

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Study Notes

Solid Materials

  • Matter is classified based on properties such as electrical, magnetic, binding energy, and thermal properties.

Electrical Properties

  • Conductors: Allow the flow of electric current.
  • Semiconductors: Have conductivity between conductors and insulators.
  • Insulators: Do not allow the flow of electric current.

Magnetic Properties

  • Paramagnetic: Weakly attracted to magnetic fields.
  • Diamagnetic: Weakly repelled by magnetic fields.
  • Ferromagnetic: Strongly attracted to magnetic fields.

Binding Energy

  • Ionic: Binding energy related to ionic bonds.
  • Valence: Binding energy related to valence electrons.
  • Metallic: Binding energy related to metallic bonds.
  • Vander Waals: Binding energy related to Vander Waals forces.

Thermal Properties

  • Thermal Conductor: Material that readily transmits heat.
  • Thermal Insulator: Material that poorly transmits heat.

Internal Building of Atoms

  • Crystalline: Atoms arranged in a repeating pattern.
  • Polycrystalline: Multiple crystals with different orientations.
  • Amorphous: Atoms arranged randomly.

Crystalline and Amorphous Solids

  • Crystalline Solids: Atoms arranged in a repeating, 3D structure (crystal lattice).
    • Have a regular, geometric shape.
    • Examples: Salt (NaCl), Diamond, Gold, Quartz (SiO2).
  • Amorphous Solids: Atoms arranged randomly with no long-range order.
    • Do not have a defined, geometric shape.
    • Examples: Glass, Plastics, Polymers, Wax.

Crystalline Materials - Criteria

  • Sudden Melting: Crystalline materials melt at a specific temperature.
  • Distinctive X-Ray Diffraction Pattern: Crystalline materials produce distinct spots in X-ray diffraction.

Crystallography

  • The science dealing with the study of solids.
  • Crystals: Solids with a repeating geometric pattern (periodic arrangement of atoms)
  • Crystal symmetry: Atoms in a lattice have symmetry.
  • Translational symmetry: Translation vector connects two identical places in the crystal lattice without changing the lattice structure

Types of Real Crystals

  • Single Crystals: The entire crystal has periodic geometric arrangement
  • Polycrystalline Materials: The periodicity of crystal structure is not continuous

Crystal Structure

  • Lattice: A three-dimensional array of points representing the arrangement of atoms.
  • Basis: The atoms associated with each point in the lattice.
  • Lattice Point: Points of the lattice that are at equivalent positions in the lattice.

Symmetry Operations

  • Translation Symmetry Operation: A displacement in a crystal lattice that leaves the pattern unchanged
  • Rotation Symmetry Operation: Rotation around an axis that leaves the lattice unchanged
  • Reflection Symmetry Operation: Reflection in a plane that leaves the lattice unchanged
  • Inversion Symmetry Operation: An inversion through a center that leaves the lattice unchanged
  • Screw Symmetry Operation: Combination of rotation and translation
  • Glide Symmetry Operation: Combination of reflection and translation

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