Chapter 3 Structure of Crystalline Solids

Question 1

energy and packing

why do atoms assemble in ordered/ crystal structures

Answer 1

Question 2

crystalline materials

Answer 2

atoms pack in periodic arrays

• metals many ceramics, some polymers

Question 3

single crystal

Answer 3

atoms are in a repeating/ periodic array over the entire material

Question 4

polycrystalline

Answer 4

comprised of many single-crystal grains

Question 5

noncrystalline (amorphous) materials

Answer 5

atoms have no periodic packing

• occurs for complex structures, rapid cooling

Question 6

unit cell

Answer 6

is a structural unit/ building block that repeated in 2D or 3D, generates the crystal structure

Question 7

7 types of crystal systems

Answer 7

In total there are seven crystal systems:

triclinic

monoclinic

orthorhombic

tetragonal

trigonal

hexagonal

cubic

A crystal family is determined by lattices and point groups.

Question 8

* quick reference *

crystal systems bravais lattices

Answer 8

Question 9

crystal structure lattice

Answer 9

A crystal lattice is the arrangement of these atoms, or groups of atoms, in a crystal.

Question 10

*quick reference *

crystal structure lattice

Answer 10

Question 11

metallic bonding

Answer 11

nondirectional, ion cores glued together by an electron cloud, hence can be arranged in dense packing schemes

Question 12

three types of unit cells

Answer 12

face-centered cubic (FCC)

body-centered cubic(BCC)

hexagonal close-packed (HCP)

Question 13

* quick reference *

BCC

Answer 13

Question 14

*quick reference *

BCC part 2

Answer 14

Question 15

atomic packing factor

Answer 15

atomic packing factor, packing efficiency, or packing fraction is the fraction of volume in a crystal structure that is occupied by constituent particles

Question 16

atomic packing factor BCC

Answer 16

Question 17

FCC lattice characteristics

Answer 17

Question 18

closed packed structure

Answer 18

refers to the most tightly packed or space-efficient composition of crystal structures (lattices)

Question 19

FCC stacking sequence

Answer 19

Question 20

hexagonal close-packed structure

stacking sequence

Answer 20

Question 21

theoretical density

Answer 21

is defined as the maximum density of a material or element that could be achieved assuming there are no voids or contaminants in the overall material

Question 22

theoretical density example

Answer 22

Question 23

densities of material classes

metals

ceramics

polymers

composites

Answer 23

metals - have close packing (metallic bonding) (often large atomic masses)

ceramics - have less dense packing (often lighter elements )

polymers - have a low packing density ( often amorphous, lighter elements )

composites - have intermediate values

Question 24

single crystals vs polycrystals

Answer 24

single crystals - properties vary with direction (anisotropic)

polycrystals - properties may/may not vary with direction

isotropic - if grains are randomly oriented

anisotropic - if grains are textured

Question 25

anisotropic vs isotropic

Answer 25

Isotropic materials show the same properties in all directions. Anisotropic materials show different properties in different directions.

Question 26

examples of isotropic materials

Answer 26

Glass, crystals with cubic symmetry, diamonds, metals

Question 27

examples of anisotropic materials

Answer 27

Wood, composite materials, all crystals (except cubic crystal)

Question 28

\* quick reference \* polycrystals (iso vs aniso )

Answer 28

Question 29

polymorphism vs allotropy

Answer 29

Polymorphism is defined as the ability of a solid material to exist in more than one form or crystal structure, whereas allotropy is defined as the property of some chemical elements to exist in two or more different forms

Question 30

point coordinates

Answer 30

Question 31

crystallographic directions

Answer 31

Refers to directions in the various crystal systems that correspond with the growth of the mineral and often with the direction of one of the faces of the original crystal itself

Question 32

linear density of an atom

Answer 32

Question 33

Miller indices

Answer 33

group of three numbers that indicates the orientation of a plane or set of parallel planes of atoms in a crystal.

Question 34

miller indices example

Answer 34

Question 35

crystallographic planes algorithm

Answer 35

1) read of intercepts of the plane with axes in terms *a, b, c* 2) take reciprocals of intercepts 3) reduce to the smallest integer values 4) enclose in parentheses no commas (hkl)

Question 36

crystallographic plane example

Answer 36

Question 37

planar density

Answer 37

is a measure of packing density in crystals.

Question 38

planar density example

Answer 38

Question 39

diffraction

Answer 39

is a powerful nondestructive technique for characterizing crystalline materials

Question 40

X-ray diffraction

Answer 40

Question 41

x-ray diffraction pattern

Answer 41

Question 42

**_Summary of this chapter_**

Answer 42