Course A- Atomic Structure of Materials

Question 1

Packing efficiency=

Answer 1

Area/volume of atoms/area/volume of unit cell

Question 2

Hexagonal close packed

Answer 2

ABAB

Question 3

Cubic close packed

Answer 3

ABCABC (also fcc)

Question 4

Simple hexagonal

Answer 4

AAA

Question 5

Simple cubic

Answer 5

AAA

Question 6

Body centred cubic

Answer 6

ABAB

Question 7

Lattice definition

Answer 7

An infinite array of points repeated periodically throughout space. The view from each lattice point is the same as from any other

Question 8

Structure=

Answer 8

Lattice+motif

Question 9

Crystal system=

Answer 9

Shape of unit cell, hexagonal/cubic/tetragonal etc.

Question 10

Lattice type=

Answer 10

No. of lattice points per cell- P, F, I- 1,4,2

Question 11

Cubic F type structures

Answer 11

ZnS(sphalerite)
CaF2(fluorite)
NaCl(halite)

Question 12

Cubic P lattice structures

Answer 12

CsCl

BaaTiO3(perovskite)

Question 13

Hexagonal P lattice structures

Answer 13

ZnS(wurtzite)

Question 14

Glide line

Answer 14

Reflective symmetry followed by a transformation

Question 15

Screw axis

Answer 15

Combination of rotations and translations, Rn
R=order of rotations
n=no of translations for one complete turn of the helix

Question 16

Trigonal system

Answer 16

A hexagonal lattice with 3 fold symmetry not 6

Question 17

Centre of symmetry

Answer 17

An atom on one side of the centre will have an equivalent atom on the other side of the the centre

Question 18

[ ]

Answer 18

Direction

Question 19

< >

Answer 19

Family of directions

Question 20

( )

Answer 20

Plane

Question 21

{ }

Answer 21

Family of planes (a form)

Question 22

Weiss Zone Law

Answer 22

hU+kV+lW=0