Crystal Structures: Building Blocks of Materials

Question 1

Which crystal structure is characterized by having atoms located at the corners and the center of a cubic unit cell?

Accepted Answer

Body-centered cubic (BCC)

Answer

Hexagonal close-packed (HCP)

Answer

Face-centered cubic (FCC)

Answer

Simple cubic

Question 2

What is the coordination number of an atom in a face-centered cubic (FCC) crystal structure?

Accepted Answer

12

Answer

4

Answer

8

Answer

6

Question 3

Which of the following metals typically exhibits a hexagonal close-packed (HCP) crystal structure at room temperature?

Accepted Answer

Magnesium

Answer

Copper

Answer

Aluminum

Answer

Iron

Question 4

The atomic packing factor (APF) represents:

Accepted Answer

The fraction of volume in a unit cell that is occupied by atoms.

Answer

The density of the material.

Answer

The number of atoms per unit cell.

Answer

The ratio of the volume of the unit cell to the volume of the atoms within it.

Question 5

A material with a high stacking fault energy will likely exhibit:

Accepted Answer

High ductility

Answer

Low ductility

Answer

Low thermal conductivity

Answer

High melting point

Question 6

Which type of point defect involves an atom missing from its regular lattice position?

Accepted Answer

Vacancy

Answer

Interstitial

Answer

Grain boundary

Answer

Dislocation

Question 7

Polymorphism refers to:

Accepted Answer

A material's ability to exist in multiple crystal structures.

Answer

The formation of alloys between different metals.

Answer

The ability of a material to change its shape under stress.

Answer

The presence of multiple grain orientations in a material.

Question 8

X-ray diffraction is a technique primarily used for:

Accepted Answer

Determining the arrangement of atoms in a crystal.

Answer

Measuring the mechanical properties of materials.

Answer

Analyzing the chemical composition of materials.

Answer

Observing the microstructure of materials.

Question 9

A slip system in a crystal structure consists of:

Accepted Answer

A specific plane and direction along which dislocations move.

Answer

The boundaries between different grains in a polycrystalline material.

Answer

Point defects within the crystal lattice.

Answer

The stacking sequence of atomic layers in a crystal structure.

Question 10

How does the grain size of a metal generally affect its yield strength?

Accepted Answer

Smaller grain size leads to higher yield strength.

Answer

Grain size does not affect yield strength.

Answer

Larger grain size leads to higher yield strength.

Question 11

Which of the following is a characteristic of a face-centered cubic (FCC) crystal structure?

Accepted Answer

Each atom has 12 nearest neighbors

Answer

Atoms form a body-centered cubic structure

Answer

Close packing factor is 0.68

Answer

Coordination number is 8

Question 12

What is the coordination number for atoms in a body-centered cubic (BCC) crystal structure?

Accepted Answer

8

Answer

12

Answer

6

Answer

4

Question 13

Which of the following materials has a face-centered cubic (FCC) crystal structure?

Accepted Answer

Copper

Answer

Zinc

Answer

Sodium

Question 14

What is the packing factor for a hexagonal close-packed (HCP) crystal structure?

Accepted Answer

0.74

Answer

0.68

Answer

0.52

Question 15

Which of the following crystal structures has the lowest atomic packing efficiency?

Accepted Answer

Simple cubic

Answer

BCC

Answer

FCC

Answer

HCP

Question 16

What is the Miller index for a plane that intersects the crystallographic axes at (3, 2, 1)?

Accepted Answer

(321)

Answer

(132)

Answer

(231)

Answer

(123)

Question 17

Which of the following crystal defects is a line defect?

Accepted Answer

Dislocation

Answer

Twin boundary

Answer

Vacancy

Answer

Grain boundary

Question 18

What is the effect of annealing on the crystal structure of a metal?

Accepted Answer

Reduces dislocation density

Answer

Decreases grain size

Answer

Increases strength

Answer

Increases atomic packing factor

Question 19

Which of the following is NOT a factor that can influence the crystal structure of a material?

Accepted Answer

Magnetic field

Answer

Composition

Answer

Temperature

Answer

Pressure

Question 20

How does the crystal structure of a material affect its properties?

Accepted Answer

Determines properties such as strength, ductility, and thermal conductivity

Answer

Crystal structure is solely determined by material properties

Answer

Material properties have no relation to the crystal structure