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Physical Chemistry 3(Chemical Bonding)

By :

Agung Nugroho Catur Saputro,S.Pd.,M.Sc

Lecture Presentation

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Crystalline Structures and X-

Ray Diffraction

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Lesson 1 :

CRYSTALLINE STRUCTURES

Penggolongan zat padat dan kristal

Ditinjau dari jenis bahan, zat padat digolongkan menjadilogam, polimer dan keramik.

Logam dapat murni, dapat pula berupa campuran yang

dikenal dengan nama paduan. Paduan dapatmembentuk senyawa, larutan padat, atau campuran.

Polimer, sebagian besar berupa senyawa organik,namun dikenal pila polimer jenis silikat.

Polimer ada yang sintetik, seperti plastik (polietilen,

poliester, dsb). Campuran secara fisik dari dua atau lebih polimer

disebutpolibend.

Campuran secara kimia dua atau lebih polimer disebutkopolimer.

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Crystal Lattice and Unit Cell

Kisi kristal dan sel satuan

Suatu kristal dapat digambarkan sbg pola berdimensi

tiga yang strukturnya berulang. Polanya dapat berupa

atom atau molekul, ataupun ion-ion.

The periodic arrangement of atoms or molecules or ions

in the crystal is called the latt ice.

Bagian terkecil dari kristal adalah sel satuan (un it cel l).

Parameter dari sel satuan dapat dinyatakan oleh sisi selsatuan (a, b, c), dan sudut diantaranya (, , ).

Atas dasar geometrinya, dikenal 7 sistem kristal. Sistem

kristal ini dapat dibagi lebih lanjut menjadi 14 kisi ruang

(kisi bravais).

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Crystal Lattice and Unit Cell

Ke-tujuh sistem kristal tersebut adalah kubus,

heksagonal, tetragonal, trigonal, ortorombik,

monoklin,dan triklin.

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Crystal Lattice and Unit Cell

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Crystal Lattice and Unit Cell

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Crystal Lattice and Unit Cell

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Crystal Lattice and Unit Cell

Structural Properties

All gemstones are crystalline structures madefrom a mixture of different elementalcompounds.

The shape of a crystal is based on the atomicstructure of these elemental building blocks.

Atoms within a mineral are arranged in anordered geometric pattern which determine its

"crystal structure". A gem's crystal structure will determine a its

symmetry, optical properties, cleavage andgeometric shape.

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Crystal Lattice and Unit Cell

Unit Cell (sel satuan)

The "unit cell" is the smallest divisible unit of amineral with symmetrical characteristics uniqueto a crystalline structure.

A structure's "unit cell" is a spatial arrangementof atoms which is tiled in three-dimensionalspace to form the crystal.

The unit cell is determined by its lattice

parameters, the length of the cell edges and theangles between them, while the positions of theatoms inside the unit cell are described by theset of atomic positions (xi,yi,zi) measured from alattice point.

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Crystal System

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The Seven Crystal Systems

1.Cubic

The Cubic crystal system is also known as

the "isometric" system. The Cubic

(Isometric) crystal system is characterized

by its total symmetry. The Cubic system has

three crystallographic axes that are all

perpendicular to each other and equal inlength. The cubic system has one lattice

point on each of the cube's four corners.

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The Seven Crystal Systems

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The Seven Crystal Systems

2. Hexagonal

The Hexagonal crystal system is has four

crystallographic axes consisting of three

equal horizontal or equatorial (a, b, and d)

axes at 120, and one vertical (c) axis that is

perpendicular to the other three. The (c) axis

can be shorter or longer than the horizontalaxes.

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The Seven Crystal Systems

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The Seven Crystal Systems

3. Tetragonal

A Tetragonal crystal is a simple cubic that is

stretched along its (c) axis to form a

rectangular prism. The Tetragonal crystal

will have a square base and top, but a

height that is taller. By continuing to stretch

the "body-centered" cubic one more Bravaislattice of the Tetragonal system is

constructed.

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The Seven Crystal Systems

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The Seven Crystal Systems

4. Rhombohedral

A Rhombohedron (aka Trigonal) has a three-dimensionalshape that is similar to a cube that has been compressedto one side. Its form is considered prismatic, as all faces

are parallel to each other. The faces that are not squareare called "rhombi." A rhombohedral crystal has six facesor rhombi, 12 edges, and 8 vertices. If all of the non-obtuseinternal angles of the faces are equal (flat sample, below),it can be called a trigonal trapezohedron.

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The Seven Crystal Systems

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The Seven Crystal Systems

5. Orthorhombic

Minerals that form in the Orthorhombic (akaRhombic) crystal system have three mutually

perpendicular axes, all with different or unequallengths.

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The Seven Crystal Systems

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The Seven Crystal Systems

6. Monoclinic

Crystals that form in the Monoclinic System havethree unequal axes. The (a) and(c)crystallographic axes are inclined toward each

other at an oblique angle, and the (b) axisisperpendicular to a and c. The (b) crystallographicaxis is called the "ortho" axis.

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The Seven Crystal Systems

7. Triclinic

Crystals that form in the Triclinic System have

three unequal crystallographic axes, all of which

intersect at oblique angles. Triclinic crystals have a1-fold symmetry axis with virtually no symmetry

and no mirrored planes.

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The Seven Crystal Systems

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Miller Indices

Kedudukan atom dalam sel satuan dinyatakan oleh koordinat x, y, zyang merupakan fraksi dari sisi sel satuan a, b, c.

Atom-atom dimisalkan sebagai titik-titik dalam kisi kristal (latt icepo in t).

Bidang yang melalui titik-titik kisi ini dapat dinyatakan denganperpotongan bidang pada ketiga sumbu a, b, c.

Misalkan bidang memotong sumbu a pada a/h, sumbu b pada b/k, dansumbu c pada c/l. bidang ini memiliki indeks (hkl) dan indeks inidisebut indeks Mil ler (Mil ler Ind ices). Jarak antara bidang = d.

Untuk sumbu sel satuan yang saling tegak lurus (ortorombik,tetragonal, kubus) berlaku :

Jadi bidang yang memotong ketiga sumbu a, b, c menurut arah positifdalam kubus dinyatakan mempunyai indeks Miller (111). Arah negatif

menurut koordinat y dinyatakan misalnya sebagai (111).

2/1

2

2

2

2

2

21

c

l

b

k

a

h

d

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Miller Indices

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Miller Indices

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Miller Indices

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Miller Indices

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X-Ray Diffraction Analysis

What is aplication of X-RayDiffraction in Chemistry?

http://localhost/var/www/apps/conversion/tmp/scratch_6/Kuliah%20XRD.pdf