Triclinic Crystal System Overview
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the effective number of atoms per hexagonal unit cell in HCP structure?

  • 6 atoms (correct)
  • 8 atoms
  • 2 atoms
  • 4 atoms

    • How much does each corner atom contribute to the total number of atoms in a unit cell?

  • 1/4 atom
  • 1/6 atom (correct)
  • 1/3 atom
  • 1/2 atom

    • What formula represents the Atomic Packing Factor (APF)?

  • APF = (N * Volume of atoms) / Volume of unit cell (correct)
  • APF = Volume of unit cell / (N * Volume of atoms)
  • APF = (Volume of unit cell) / N
  • APF = N / Volume of atom

    • Which atoms contribute to the effective number of atoms in HCP structure?

    <p>Corner, face centered, and internal atoms</p> Signup and view all the answers

    What is the APF in HCP structure indicative of?

    <p>It has a higher density than BCC structure.</p> Signup and view all the answers

    What is the contribution of each face centered atom in HCP structure per unit cell?

    <p>1/2 atom</p> Signup and view all the answers

    Which of the following metals crystallizes in HCP structure?

    <p>Magnesium</p> Signup and view all the answers

    What value must be used as 'N' in the APF formula for HCP?

    <p>6 atoms</p> Signup and view all the answers

    What is a group of equivalent directions in crystallography called?

    <p>Direction family</p> Signup and view all the answers

    How are families of directions indicated in crystallography?

    <p>Angle brackets</p> Signup and view all the answers

    What is the first step in determining the indices for a crystallographic plane?

    <p>Position the plane in a convenient position</p> Signup and view all the answers

    What indicates a negative direction in the Miller indices notation?

    <p>A bar above the number</p> Signup and view all the answers

    If a plane is parallel to an axis, what is its intercept considered?

    <p>Infinite</p> Signup and view all the answers

    Which of the following is true regarding crystallographic planes?

    <p>They can be expressed using Miller indices.</p> Signup and view all the answers

    What is step 3 in the process of finding Miller indices?

    <p>Take the reciprocals of the intercepts</p> Signup and view all the answers

    What must be done to the intercepts before enclosing them in parentheses?

    <p>Multiply or divide to get whole numbers</p> Signup and view all the answers

    What is the first step in defining any direction of a vector?

    <p>Position the vector so it passes through the origin.</p> Signup and view all the answers

    How are the projections of a vector on the X, Y, and Z axes determined?

    <p>By taking intercepts of the vector on the axes.</p> Signup and view all the answers

    What is the final outcome after computing the Miller indices from a vector's projections?

    <p>A set of whole numbers enclosed in square brackets.</p> Signup and view all the answers

    In the Miller indexing system, how is a negative direction represented?

    <p>By placing a bar above the appropriate integer.</p> Signup and view all the answers

    When finding the Miller indices, what transformation is applied to ensure the values are whole numbers?

    <p>They are multiplied or divided by a common number.</p> Signup and view all the answers

    What are the intercepts for the given vector when $a = b = c$?

    <p>$1/2, 1, 0$</p> Signup and view all the answers

    What represents a 'step' moved parallel to an axis when pinning down a vector in 3D space?

    <p>The component of the vector along that axis.</p> Signup and view all the answers

    How are the directional indices represented according to the conventions used in the Miller system?

    <p>As whole numbers in square brackets.</p> Signup and view all the answers

    What are the Miller indices for a plane that is perpendicular to the Z axis?

    <p>(001)</p> Signup and view all the answers

    Which of the following is true about point imperfections in crystals?

    <p>They are a result of original crystallization.</p> Signup and view all the answers

    Which type of crystal defect is defined as a three-dimensional imperfection?

    <p>Volume imperfections</p> Signup and view all the answers

    What impact can Schottky and Frankel point defects have on metals?

    <p>They influence electrical and magnetic properties.</p> Signup and view all the answers

    What is a characteristic of an ideal crystal?

    <p>Each atom has identical surroundings.</p> Signup and view all the answers

    How can crystal defects be reduced?

    <p>By controlling the temperature during crystallization.</p> Signup and view all the answers

    Which type of imperfection in a crystal lattice is classified as a one-dimensional defect?

    <p>Line imperfections</p> Signup and view all the answers

    What causes point defects to form during the crystal lattice formation?

    <p>Changes in atomic vibrations.</p> Signup and view all the answers

    Which crystal system has the property that all axial lengths are unequal and all interaxial angles are also unequal?

    <p>Triclinic</p> Signup and view all the answers

    What is the total effective number of atoms per unit cell in a body-centered cubic (BCC) structure?

    <p>2 atoms</p> Signup and view all the answers

    In which crystal structure do the atoms located at the corners of the cubic cell touch the face-centered atoms?

    <p>Face-centered cubic (FCC)</p> Signup and view all the answers

    Which of the following statements is true regarding the interaxial angles of the orthorhombic crystal system?

    <p>All angles are 90 degrees</p> Signup and view all the answers

    Which of the following metals crystallizes in a body-centered cubic (BCC) structure?

    <p>Iron (α-Fe)</p> Signup and view all the answers

    Which crystal system is also known as Cubic Close Packed (CCP)?

    <p>Face-centered cubic (FCC)</p> Signup and view all the answers

    How many corner atoms contribute to the effective atom count in a body-centered cubic unit cell?

    <p>8 corner atoms</p> Signup and view all the answers

    Which of the following characterizes the tetragonal crystal system?

    <p>a=b≠c and α=β=γ=90</p> Signup and view all the answers

    Study Notes

    Triclinic Crystal System and Summary of Crystal Systems

    • Triclinic crystals have variable axial lengths where a≠b≠c and all interaxial angles (α, β, γ) are unequal and ≠90°.
    • The seven crystal systems include:
      • Cubic: a = b = c; α = β = γ = 90°
      • Tetragonal: a = b ≠ c; α = β = γ = 90°
      • Hexagonal: a = b ≠ c; α = β = 90°, γ = 120°
      • Orthorhombic: a ≠ b ≠ c; α = β = γ = 90°
      • Rhombohedral: a = b = c; α = β = γ ≠ 90°
      • Monoclinic: a ≠ b ≠ c; α = β = 90°, γ ≠ 90°
      • Triclinic: a ≠ b ≠ c; α ≠ β ≠ γ ≠ 90°

    Body Centered Cubic Structure (BCC)

    • Atoms located at eight corners of the cubic cell and one at the geometric center.
    • Total atoms per BCC unit cell is 9 (8 corner + 1 center).
    • Corner atoms contribute 1/8 each, and the center atom contributes 1, leading to:
      • Effective number of atoms in BCC = 2 (1 from corners + 1 from center).
    • Metals such as Chromium, α-Fe, δ-Fe, Molybdenum, and Lithium exhibit BCC structure.

    Face Centered Cubic Structure (FCC)

    • Atoms are situated at the eight corners and six face centers of the cubic cell.
    • No atoms in the body center unlike BCC.
    • Effective number of atoms in FCC is calculated as:
      • 12 corner atoms contributing 1/6 each + 2 face-centered atoms contributing 1/2 each + 3 internal atoms = 6 total.
    • Metals such as Magnesium, Zinc, and Graphite crystallize in the FCC structure.

    Atomic Packing Factor (APF)

    • Indicates the volume percentage occupied by atoms in a unit cell.
    • Formula for APF: ( APF = \dfrac{N \times V_{atom}}{V_{cell}} \times 100 )
      • Where N = effective number of atoms, ( V_{atom} ) = volume of a spherical atom, and ( V_{cell} ) = volume of the unit cell.

    Miller Indices

    • Used to denote crystallographic directions and planes.
    • Directions expressed as [uvw]; negative directions indicated with bars over integers.
    • Families of equivalent directions shown in angular brackets.
    • Indices derived from steps to intersections on axes:
      • For a direction: determine intercepts, take reciprocals, convert to whole numbers.
      • For a plane: determine intersections, take reciprocals, convert to whole numbers.

    Crystal Imperfections

    • Ideal crystals have perfect atomic arrangements; real crystals have imperfections due to finite size and surface boundaries.
    • Types of crystal defects:
      • Point Imperfections: Atoms missing or extra (e.g., Schottky and Frankel defects affecting properties like conductivity).
      • Line or Linear Imperfections: Affecting rows of atoms.
      • Surface or Plane Imperfections: Seen on boundaries.
      • Volume Imperfections: Affect entire volumes of the crystal.
    • Formation causes include irradiation, plastic deformation, quenching, and increased temperature leading to distortions in crystal lattice.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz covers the Triclinic crystal system and provides a summary of different crystal systems, including their axial lengths and interaxial angles. Test your knowledge of crystal structures and understand the unique properties of the Triclinic system.

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser