Crystal Structures and Types of Solids in Materials Science
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PROF. DR. B. J. LOKHANDE
SCHOOL OF PHYSICAL SCIENCES
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•
In
a
Crystalline
solid
, atoms are
arranged in
an
orderly
manner. The atoms
are
having long range
order.
–
Example
:
Iron, Copper and other
metals,
NaCl
etc.
•
In
an
Amorphous
solid
,
atoms
are not
present
in an orderly
manner. They are
randomly
arranged.
–
Example
:
Glass
•
Non
dense,
random
packing
•
Dense,
regular
packing
r
Energy
typical
neighbor
bond
length
typical
neighbor
bond
energy
En
e
r
g
y
r
typical
neighbor
bond
length
typical neighbor
bond
energy
Dense,
regular-packed
structures
tend
to
have
lower
energy.
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Crystalline
material is
a
material comprised
of
one
or
many
crystals.
In
crystal,
atoms or
ions
show
a
long-range periodic
arrangement.
Single
crystal
is
a
crystalline
material
that
is made of
only
one
crystal
(
no grain
boundaries).
Grains
are the crystals in
a
polycrystalline
material.
Polycrystalline
material
is
a
material comprised
of
many crystals (
single-crystal
material
that
has
only
one
crystal).
Grain boundaries
are
regions
between
grains of
a
polycrystalline
material
.
A
unit
cell
is the smallest part of the
unit cell,
which when
repeated
in
all three
directions, reproduces the
lattice
.
All
unit cells may
be
described
via these vectors
and angles.
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N
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T
CE
L
L
OF
BCC
LA
T
T
I
CE
•
F
e
(
U
p
t
o
91
0
0
C
an
d
f
r
o
m
14
0
1
0
C
to
Melting Point),
W,
Cr,
V,
\
UNIT CELL
OF
FCC
LATTICE
•
Al,
Cu,
Ni,
Fe
(910
0
C-1401
0
C)
UNIT CELL
OF
HEXAGONAL CLOSED PACKED
(HCP)
•
Zn,
Mg
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S
•
Miller Indices are used to
represent
the directions and the
planes
in a crystal
•
Miller Indices is a
group
of
smallest
integers
which
represent a
direction or a plane
z
y
z
[1
1
1]
[
0
1
2
]
x
[
0
2
1]
y
[111]
[100]
[
11
0
]
b
x
M
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Select any point on the direction line other than the origin Find out the
coordinates of the point in terms of the unit vectors along different axes.
Specify negative coordinate with a bar on top Divide the m by the unit vector
along the respective axis.
Convert the result into the smallest integers by suitable multiplication or
division.
Crystal structures in materials science involve the arrangement of atoms in solids, with examples of crystalline and amorphous solids like metals and glass. Explore concepts like energy packing, definitions of crystalline materials, unit cells, BCC and FCC lattices, HCP structures, and Miller Indices in crystallography.
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Presentation Transcript
CRYSTAL STRUCTURE PROF. DR. B. J. LOKHANDE SCHOOL OF PHYSICAL SCIENCES
TYPES OF SOLIDS In a Crystalline solid, atoms are arranged in an orderly manner. The atoms are having long range order. Example : Iron, Copper and other metals, NaCl etc. In an Amorphous solid, atoms are not present in an orderly manner. They are randomly arranged. Example : Glass
ENERGY AND PACKING Non dense, randompacking Energy typical neighbor bond length typical neighbor bond energy r Energy Dense, regular packing typical neighbor bond length r typical neighbor bond energy Dense, regular-packed structures tend to have lower energy.
SOME DEFINITIONS Crystalline material is a material comprised of one or many crystals. Incrystal, atoms or ions show a long-range periodic arrangement. Single crystal is a crystalline material that is made of only one crystal (no grain boundaries). Grains are the crystals in a polycrystalline material. Polycrystalline material is a material comprised of many crystals (single-crystal material that has only one crystal). Grain boundaries are regions between grains of a polycrystalline material. A unit cell is the smallest part of the unit cell, which when repeated in all three directions, reproduces the lattice.
UNIT CELLS AND UNIT CELL VECTORS All unit cells may be described via these vectors and angles.
UNIT CELLOF BCC LATTICE Fe (Up to 9100C and from 14010C to Melting Point), W, Cr, V, \
UNIT CELL OF FCC LATTICE Al, Cu, Ni, Fe (9100 C-14010C)
MILLER INDICES Miller Indices are used to represent the directions and the planes in a crystal Miller Indices is a group of smallest integers which represent a direction or a plane y z y z x [021] [111] [012] [111] x [100] [110] b
MILLER INDICES Select any point on the direction line other than the origin Find out the coordinates of the point in terms of the unit vectors along different axes. Specify negative coordinate with a bar on top Divide the m by the unit vector along the respective axis. Convert the result into the smallest integers by suitable multiplication or division.
