noc19-cy16 Lecture 01-Solid State and Solid State materials

Summary

This lecture introduces the fundamentals of solid state chemistry, exploring the nature of solid states and their classifications. It distinguishes between crystalline, amorphous, and quasicrystalline solids, highlighting their structural differences. The lecture also delves into various types of solids, including metallic, covalent network, ionic, and molecular crystals, each with unique properties. Furthermore, it underscores the significance of solid state materials in modern applications, from electronics to energy storage, and the potential for creating advanced materials with tailored properties.

Takeaways

• 📘 The solid state is one of the three fundamental states of matter, alongside liquids and gases, and is characterized by particles that are closely packed and maintain a definite shape and volume.
• 🧊 Solids are stable at lower temperatures and can transition to liquids and then gases as temperature increases.
• 🏺 Most materials encountered in everyday life are solids, including a significant portion of the human body.
• 💎 Solids can be categorized into crystalline, amorphous, or quasicrystalline based on the arrangement of their constituent particles.
• 🔬 Crystalline solids exhibit a perfectly ordered structure both locally and globally, whereas amorphous solids lack this long-range order, and quasicrystals have non-periodic spatial ordering.
• 🔑 Metallic solids are characterized by their ductility, high density, and good electrical conductivity, with valence electrons that are free to move throughout the structure.
• 💠 Covalent network crystals, such as diamond or silicon, consist of a network of strong covalent bonds, making them very hard but also brittle.
• 🌐 Ionic crystals, like sodium chloride, are composed of positive and negative ions held together by ionic bonds, resulting in high melting points and brittleness.
• 🌫 Molecular crystals are formed by molecules arranged in a regular pattern, held together by weaker forces like van der Waals interactions, leading to low melting points and softness.
• 🌌 The study of solid-state chemistry is crucial for understanding the properties of materials and for developing new materials with improved characteristics.
• 🛠️ Solid-state materials are extensively used in various applications, including electronics, magnetic materials, photonics, catalysis, energy storage, and metamaterials with extraordinary properties.

Q & A

What are the three states of matter, and how do they differ in terms of particle arrangement?

The three states of matter are solid, liquid, and gas. In solids, particles are closely packed and have a fixed shape and volume. Liquids have particles that are less closely packed than in solids, take the shape of the container but maintain a definite volume. Gases have particles that are widely spaced, take the shape and volume of the container, and are easily compressible.

What is the difference between crystalline, amorphous, and quasicrystalline solids?

Crystalline solids have a perfectly ordered spatial arrangement with identical local and global structures. Amorphous solids lack this long-range order and have a disordered structure. Quasicrystalline solids exhibit spatial ordering that is not periodic, meaning they have local order without translational symmetry.

Why are most materials in everyday life considered to be solid?

Most materials in everyday life are solid because they are stable at room temperature and are easily manipulated and used in their solid state. Solids have a definite shape and volume, making them suitable for various applications and structures.

What are some examples of amorphous solids?

Examples of amorphous solids include glasses, polymeric solids, and wax. These materials do not form regular crystal lattices and tend to collapse into powders rather than forming large crystals.

What is the significance of the discovery of quasicrystals in 1980?

The discovery of quasicrystals in 1980 challenged the existing understanding of crystallography by showing that materials could have long-range order without periodicity. This discovery expanded the classification of solid materials and opened new avenues for material science research.

What are the key characteristics of metallic solids?

Metallic solids are characterized by their deformability, high density, and good electrical conductivity. They have a lustrous appearance and are typically ductile, allowing them to be shaped into wires. The structure of metallic solids involves a lattice of atomic cores with valence electrons that are free to move throughout the material, contributing to their conductivity.

How do covalent network crystals differ from metallic solids in terms of bonding?

Covalent network crystals, like diamond or silicon, are characterized by strong, directional covalent bonds between atoms. This results in a hard, brittle material that does not conduct electricity well. In contrast, metallic solids have metallic bonding with delocalized valence electrons, which allows for ductility and electrical conductivity.

What are the properties of ionic crystals, and how do they form?

Ionic crystals are composed of positively and negatively charged ions arranged in a regular, repeating pattern. They typically have high melting points and are hard but brittle. The ionic bonds in these crystals are very strong, leading to properties such as high electrical conductivity when molten and the formation of lattice structures.

What are molecular crystals, and how do their properties differ from other types of crystals?

Molecular crystals are composed of molecules arranged in a regular lattice. The interactions between these molecules are typically weak, such as van der Waals forces or pi-pi stacking interactions. As a result, molecular crystals have low melting points, are soft, and do not conduct electricity well.

Why is the study of solid-state chemistry important for the development of modern materials?

The study of solid-state chemistry is crucial for understanding the properties and behavior of materials at the atomic and molecular levels. This understanding allows scientists to design and develop new materials with improved or tailored properties for various applications, such as electronics, energy storage, and photonics.

What are some examples of solid-state materials used in everyday life and their applications?

Examples of solid-state materials used in everyday life include semiconductors in electronic devices, magnetic materials in data storage, photonic materials in optical fibers and lasers, catalysts in chemical reactions, energy materials like lithium-ion batteries, and super materials such as superconductors and metamaterials with unique properties.

Outlines

00:00

🧊 Introduction to Solid State Chemistry

The lecture introduces the concept of solid state chemistry, defining the solid state as one of the three fundamental states of matter, alongside liquids and gases. It emphasizes the prevalence of solids in everyday life and their importance in the human body and various applications. The lecturer explains the transition from solid to liquid to gas with increasing temperature and introduces the concepts of crystalline, amorphous, and quasicrystalline solids, highlighting their structural differences and providing examples of each.

05:10

📐 Understanding Crystalline and Quasicrystalline Structures

This section delves into the specifics of crystalline solids, which exhibit periodic and translationally invariant structures where atoms are arranged in a repeating pattern. The lecture contrasts this with quasicrystals, which, although ordered, lack periodicity. Examples of quasicrystals, such as aluminum-manganese alloys, are given, and the unique 2-dimensional quasicrystal tiling is used to illustrate the concept of non-periodic order.

10:10

🔬 Classification of Solids Based on Particle Interactions

The paragraph discusses the classification of solids based on the nature of interactions between their constituent particles. It covers metallic solids, known for their deformability, conductivity, and lustrous appearance, attributed to a 'sea' of delocalized valence electrons. Covalent network crystals, such as diamond and silicon, are highlighted for their strong directional covalent bonds, leading to hardness and brittleness. The summary also touches on the historical significance of understanding metals in the development of solid-state science.

15:12

🌐 Exploring Ionic, Molecular, and Super Materials

This part of the lecture explores ionic crystals, formed by the orderly arrangement of positive and negative ions, which result in strong ionic bonds and high melting points. Molecular crystals, composed of discrete molecules held together by weaker forces like van der Waals interactions, are described as having low melting points and being soft. The paragraph also introduces 'super materials' with extraordinary properties, such as superconductors and metamaterials with negative properties, illustrating the breadth of materials studied in solid-state chemistry.

20:18

🚀 Applications and Significance of Solid State Materials

The final paragraph underscores the importance of solid-state chemistry in modern applications, from electronic and magnetic materials in semiconductor devices and organic electronics to photonic materials used in lasers and optical fibers. The role of solid-state materials as catalysts in industrial chemical reactions is highlighted, along with their use in energy materials like lithium-ion batteries and hydrogen storage. The paragraph concludes by emphasizing the ability to manipulate solid-state materials to create 'win-all' materials that are both biocompatible and environmentally friendly.

Keywords

💡Solid State

The 'Solid State' refers to one of the three fundamental states of matter, characterized by particles that are closely packed together and have a fixed shape and volume. In the video, it is the primary subject of the lecture, with a focus on understanding the nature and properties of solids, which are essential for the study of solid-state chemistry.

💡Crystalline Solid

A 'Crystalline Solid' is a type of solid where the atoms, molecules, or ions are arranged in a highly ordered, repeating pattern extending in all three spatial dimensions. The script mentions that crystalline solids have both local and global structures that are identical, making them a key subject in the study of solid-state materials.

💡Amorphous Solid

An 'Amorphous Solid' is a solid that lacks a long-range order in its molecular or atomic structure. The script describes amorphous solids as having a disordered structure where the constituents are very close to each other but do not exhibit the same level of ordering as in crystalline solids, with examples including glass and wax.

💡Quasi Crystal

A 'Quasi Crystal' is a phase of matter that has a spatial ordering but is not periodic, discovered in the 1980s. The script explains that quasicrystals have an ordered structure, but unlike crystalline solids, their arrangement does not repeat periodically, which is a unique characteristic in the study of solid-state materials.

💡Metallic Solids

In the context of the video, 'Metallic Solids' are a class of solids characterized by their ability to deform, high electrical conductivity, and a lustrous appearance. The script discusses metallic bonding, where valence electrons are free to move throughout the structure, contributing to the properties of metals.

💡Covalent Network Crystals

A 'Covalent Network Crystal' is a type of solid where atoms are bonded together in a continuous network by covalent bonds. The script uses diamond as an example, where each carbon atom is bonded to four others, creating a strong and hard material, but also brittle due to the directional nature of covalent bonds.

💡Ionic Crystals

An 'Ionic Crystal' is composed of positively and negatively charged ions held together by ionic bonds. The script explains that ionic crystals, such as sodium chloride, have high melting points and are hard but brittle due to the strong electrostatic forces between ions.

💡Molecular Crystals

A 'Molecular Crystal' consists of molecules arranged in a regular pattern. The script notes that the interactions between molecules in a molecular crystal are typically weak, such as van der Waals forces, resulting in low melting points and soft materials, with ice being an example.

💡Solid-State Materials

'Solid-State Materials' encompass a wide range of materials studied in solid-state chemistry, which are of significant interest due to their applications in modern technology. The script highlights various types of solid-state materials, including electronic, magnetic, photonic, and energy materials, emphasizing their importance in everyday life and technological advancements.

💡Superconductors

A 'Superconductor' is a type of solid-state material that exhibits zero electrical resistance, allowing for lossless transmission of electricity. The script categorizes superconductors as 'super materials' due to their extraordinary property of having extremely low resistance, which is crucial for applications in energy transmission and magnetic levitation.

💡Meta Materials

'Meta Materials' are artificially structured materials with unique properties not found in nature, such as negative refractive index or negative temperature coefficient of resistance. The script describes meta materials as having 'negative transport properties' and being a class of 'super materials' with special characteristics engineered through the arrangement of different materials.

Highlights

Introduction to the nature of the Solid State and Solid State Materials.

Solid state of matter is one of the three states, alongside liquids and gases.

Solids are stable at low temperatures and transition to liquid and gas states as temperature increases.

Most everyday materials and the human body are predominantly solid.

Solids can be classified as crystalline, amorphous, or quasi-crystalline based on their atomic arrangement.

Crystalline solids exhibit a perfectly ordered structure with identical local and global arrangements.

Amorphous solids lack a perfect order, with components closely packed but disordered.

Quasi-crystals were discovered in 1980 and feature ordered but non-periodic structures.

Metallic solids are characterized by their deformability, high density, and good electrical conductivity.

Metallic bonding involves valence electrons freely roaming a lattice formed by atomic cores.

Covalent network crystals, like diamond, feature strong directional covalent bonds.

Covalent network crystals are hard, brittle, and poor conductors of electricity.

Ionic crystals consist of positive and negative ions with strong ionic bonds.

Molecular crystals are formed by stable molecules held together by weak van der Waals forces.

Solid state chemistry is crucial for understanding the properties and development of modern materials.

Examples of solid state materials include electronic, magnetic, photonic, catalytic, energy storage, and super materials.

Meta-materials and win-all materials are recent discoveries with extraordinary and tunable properties.

Solid state materials can be manipulated for biocompatibility and environmental friendliness.

Conclusion summarizing the basic properties and study framework of the solid state of matter.

Transcripts

Today, we will start the first week and the first lecture of this course on Solid State

Chemistry.

So, in today’s lecture I will be talking about the nature of the Solid State and Solid

State Materials.

So, we will start this lecture, today’s lecture will be on solid state and solid state

materials.

Now, what is the solid state of matter?

So, solid state of matter intuitively you learnt that it is one of the three states

of matter.

So, matter exists in typically in three states – solids, liquids and gas.

And, we usually think that if you had a container and you had a solid, so, a solid will occupy

some region of the container that it is put in.

So, this will be a solid.

A liquid on the other hand you expect it to take the shape of the container and it will

occupy some region, I will just show it in this way that this is a region occupied by

the liquid and I will show the liquid has lot of particles that are fairly close to

each other, but not as close as in a solid.

So, that is your liquid and it will take the shape of the container.

A gas on the other hand you say that it has very it has relatively few number of particles

and so, it will typically you will find the gas particles all over the container and like

a liquid it will also take the shape of the container, but you will find that there are

very few particles in the gas.

So, these are the typical three states of matter that you always learn and so, solid

is one state of matter and it is stable at low temperatures as you increase the temperature

you go from solid to liquid to gas.

And, most things in everyday life are solids.

So, all around us we have solid materials that we deal with.

In fact, our own body for large part of it is solid, okay; there is also liquid in our

body, but a large part of it is solid and in any case most of the materials that we

do that we use our solids.

And, you can take almost all materials including mixtures you can take pure compounds and mixtures

and you can solidify them.

So, if you have something that is a liquid you cool it and it turns into solid.

So, this is what we know about solids, okay.

But, there are some other characteristics of solids okay, which are quite interesting.

So, solids can be either crystalline, amorphous or quasi crystalline, okay.

So, a crystalline solid has perfectly ordered spatially and has a local structure and a

global structure, which are identical.

So, in the sense in a crystalline solid if you would have let us say if these are the

atoms of the solid, they would be perfectly arranged in some structure ok, and this is

I am showing it in 2-dimensions, but you would have a perfect arrangement of constituent

atoms or molecules in a crystal okay.

So, that is what crystalline solid will look.

Everything is perfectly arranged.

I am just showing one example here of a centered square lattice okay.

This is in 2-dimensions, but we will see lot more about crystals later.

In an amorphous solid the constituents of the solid are disordered, they form a disordered

structure.

So, you do not have a perfect ordering, ok; you might have something like…..you have

a solid like, but you have things that are not perfectly ordered, ok.

So, that would be an amorphous solid.

So, things are very close to each other the components of the amorphous solid are very

close to each other and so, and so, the atoms if this is made of atoms then those atoms

are not able to move much, okay.

However, it is not ordered, there is not much ordering of these atoms, okay.

So, it is a solid, but it is not perfectly ordered and that is what you call amorphous

solid.

It is a disordered structure some examples of amorphous solids are glasses you can have

polymeric solids ok, you can have for example, wax is an amorphous solid.

You can have several different examples of amorphous solids.

Typically these amorphous solids they collapse into powders and you cannot form big crystals

with them.

A third relatively recent discovery is that of quasi crystals this was these were discovered

around 1980, okay.

So, they were discovered in 1980 and these are in quasi crystals there is a spatial ordering,

but it is not periodic.

So, in a crystalline solid the arrangement is periodic; that means each atom sees exactly

the same surroundings or each constituent, okay.

It need not be an atom, but whatever unit of the crystal it sees exactly the same surroundings

as any other constituent, okay.

So, it is periodic, okay.

So, that means, if you move, if you change let us say you are looking in this region

let us say you look at the crystal in this region and imagine that you just translate

okay, and now, you start looking let us say in this region, the crystal will look exactly

identical.

Similarly, you translate into this region the crystal will look identical, okay.

So, there is a translational invariance in a crystal.

So, this is not there in a quasi crystal.

So, you say it is ordered spatially, but it is not periodic and this is being observed

in some alloys like aluminum-manganese alloy, aluminum-manganese-silicon alloy.

So, just to show you what would something that is ordered, but not periodic look like

okay, this is a picture of a 2-dimensional quasi crystal it is….it is called it is

referred to as a tiling, okay.

This is referred to as a tiling and it is in 2D, okay.

So, it is a 2-dimensional tiling okay, and you can see that there is an order in the

sense that you go around each point you see some sort of arrangement some sort of very

regular arrangement.

So, it is completely ordered, but it is not periodic.

I mean you cannot you do not see you cannot translate this piece of the crystal for some….somewhere

and see the same ordering, okay.

So, this is an example of a quasi crystal and this is a very special class of material.

In most of this course I am going to be talking about crystalline solids.

Almost…almost the entire course we are going to be talking about crystalline solids.

Though I should emphasize that there is a lot of interest in amorphous materials and

by no means this is the entire spectrum of all solid materials, okay.

So, but, for this course we will be mostly focusing on crystalline solids and we will

be seeing how to understand this spatial ordering in the…in the crystal, okay.

The other way to look at different types of solids is to think of them as based on the

nature of the interactions between the constituent particles, okay.

So, you can think of metallic solids, okay.

This is example of all metals like iron, cobalt, nickel, zinc, okay.

These typically are deformable, okay, you there ductile, okay and they have high density

they are good conductors, okay.

What I mean by deformable is that….is that you can you can stretch them, you can make

them into wires and so on.

They are typically good conductors of electricity and they typically have this lustrous look.

And, in fact….in fact historically it is to explain the properties of metals.

What makes metallic solids have these properties that are lot of science of solid state was

developed, okay.

One characteristic of metallic solids is that they in the…if you look at a metallic solid,

let say iron or let say copper; if you are looking at copper, okay.

If you look at the structure of copper what you will find is that you will see all these….the

core of copper, okay.

When I say the core of copper it is a nucleus of copper and all the electrons except the

valence electrons okay, they form some sort of lattice.

They form this….this crystal structure okay, and in this you have the valence electrons

are essentially the valence electrons are freely roaming around in this lattice formed

by the core of each atom.

So, this sort of bonding, where you have the valence electrons, essentially going all around

the entire crystal okay.

This is sometimes referred to as metallic bonding and this is a characteristic of metallic

solids.

We will of course, discuss this in a lot more detail as we go on, but I just wanted to tell

you the different kinds of crystals.

So, these metallic solids have this kind of picture okay.

So, this is this would be a metallic solid or a metallic crystal, okay.

So, the other kind of solids that we often deal with or what are called as covalent network

crystals okay, and the best example is silicon or diamond okay, where essentially you have

covalent bonds, okay.

So, if you take diamond, okay for example, you have a carbon atom oaky, that is covalently

that is tetrahedrally bonded to four other carbon atoms okay and now each of these is

also tetrahedrally bonded to four others.

And, essentially you form a network structure of this whole solid, okay.

So, so you form an extended covalent network that is shown this way, okay.

Again I am not…..okay.

So, diamond is a good example, okay also silicon forms a diamond solid, okay.

What is important the important difference between a covalent network crystal and metallic

solid is that the bonds are covalent bonds.

So, these are directional.

So, covalent bonds have a preferred direction okay, and this is one very distinct feature

of covalent network crystals, okay.

So, and these are fairly strong, these are also very strong bonds.

Typically covalent bonds are quite strong.

In addition to things like silicon or carbon or in diamond form you can also have oxides

like silica; quartz is a form of silica, which is also a network solid.

You can have transition metal oxides.

So, these are also covalent solids, okay.

One feature of lot of these covalent networks solids is that they are very hard and I emphasize

the word very because…because the whole structure is a network solid often some of

the hardest materials are covalent network crystals, okay.

But, they are brittle; you cannot deform them easily unlike in the case of metallic solids,

okay.

And, needless to say they are not typically they are not good conductors of electricity

and they do not have the luster that metals have, okay.

And, they are typically much lower density than metallic solids.

A third class of crystals are ionic crystals, okay.

So, these are basically the constituents are positive and negative ions, okay.

So, for example, if you take sodium chloride; sodium chloride has a…has a positive sodium

ion and a negative chloride ion.

So, if you see the sodium chloride crystal you have the sodium ions, okay that I am denoting

by blue sodium plus ions and you have chloride ions okay, and the whole structure is formed

by…by repeating by an ordered arrangement of these two ions, okay.

So, it looks…..so, you have an order and I am just showing you 2-dimensions, but it

is actually ordered in 3-dimensions.

And, so, now, what happens is that these bonds between sodium and chloride, okay.

They are ionic bonds and they are very strong bonds okay, they are very strong bonds, okay.

So, what happens is that it has a very these ionic solids typically have high melting points,

okay.

They can be hard, but they end up being very brittle.

You cannot deform them easily like your metallic solids.

So, actually the ductility of metallic solids comes from the nature of the metallic bond.

Then there is another class of crystals, which are the molecular crystals okay, such as where

the constituents are not atoms, okay.

So, the constituents of the crystals are not atoms, but in fact, they are molecules you

can have a water molecule okay, you can have ice, which is a crystal of water molecules,

you can have benzene molecules combined together to form a crystal, you can have almost all

organic molecules if you cool them enough they form solids and they crystallize.

So, what is special is that…is that I mean….I mean when you molecule, which I will denote

by this shape okay, and you are essentially forming a crystal using this molecule.

So, so, you have a whole….you have lots of these molecules arranged in some regular

order to form a crystal, okay.

Now, what you would expect is that if these are stable molecules then the interaction

between these two the interactions between these stable molecules will actually be very

weak, okay.

There will be typically van der Waals interactions will be there if we….if we if we have neutral

molecules, if we have benzene molecules they will have either van der Waals or they will

have pi-pi stacking interactions, but they are much weaker than the actual covalent or

ionic bonds that are there in the covalent solids or the ionic solids.

So, therefore, they……these will have very low melting point okay, because these they

can easily be dissociated and they will be very soft, okay.

So, what I want to say is that all these different kinds of crystals okay, they are very different

in properties, but they still share certain features and the features that they share

is that they all have some unit, which is perfectly arranged on a lattice okay, and

it is this feature of the crystal okay, that we will be studying over the next 12 weeks

okay.

Now, incidentally you know this I am may I mentioned ice has some molecular crystals.

I should say that there is a lot of the structure of ice and the…..both the crystal structure

and the crystal shape of ice is something that has attracted lot of interest and from

several groups and it is…it is a topic of both scientific and artistic interest, okay.

So….so I recommend all of you to visit this website snow crystals dot com just to see

how you can get crystals ice crystals of many different shapes, okay.

And, I mean….I mean we you could just take a look at it and appreciate the beauty that

is there in all these crystal shapes, many of them are naturally occurring, okay.

Now, one of the reasons why solid state chemistry is of lot of interest in especially in recent

times is that many of the materials especially the modern materials that we use are materials

that are solid state materials.

And, one of the things about solid state materials is that…is that you can really if you understand

the solid state you can actually understand the origin of the properties and you can make

better materials with better properties.

This is…this has been the driving force for a lot of research in solid state in solid

state chemistry, okay.

So, I will just show some examples, these are by no means all the types of solid state

materials, but these are some example of solid state materials that are actually used in

day to day life and many of them you use them without even realizing that they are being

used, okay.

So, there are a whole range of solid state materials, which I have put is basically electronic

and magnetic materials, okay.

So, right from semiconductor devices there is nowadays there is a lot of interest in

organic electronics, okay.

So, I mean you might have seen some advertisements, where they say that your TV screen is organic

LEDs and there is interest in flexible electronics, where you have electronic materials, but they

are flexible and, these have several applications.

There is also interest in printable electronics and then there is also a huge range of materials,

which are magnetic materials, all kinds of magnetic materials are of interest.

Then there is a whole class of materials, which I would classify as photonic materials,

okay.

So, these are various they have various interesting optical properties for example, the materials

that are used for lasers, for LEDs, fiber optics, wave guides, optical readers etcetera.

Then there is a whole class of materials, which are used as catalysts…which are used

as catalysts for various reactions.

So, for example, the car exhaust, okay.

So, that that has a catalyst, okay which consists of lead okay, and again, again there is lot

of research on developing better catalysts, but in fact…..in fact industrially almost

every chemical reaction, okay is carried out in the presence of catalysts and many of these

catalysts are actually solid state materials, okay.

So, the whole field of molecular synthesis involves catalysts and which are…which are

solid state materials.

Then, there is a class of materials, which are….again…again recently there is a lot

of interest in these energy materials and here….here….here I am particularly referring

to batteries like lithium ion batteries okay, again this is another solid state material.

Then there are material for hydrogen storage, okay.

So, there are because….because if you can store hydrogen you can use hydrogen as a fuel

to do various activities like running cars or something and so, you need to store the

hydrogen and there are some solid state materials that are used for hydrogen storage.

Another class of materials, which people are discovering more and more is what are called

these super materials; I am calling them super materials because they have extraordinary

properties, okay.

For example, a superconductor, okay has extremely low resistance.

So, again….again this is a solid state material, a super capacitor you can have a super capacitor

you can have a giant magneto-resistic…. resistant materials the GMR materials, which

are used in lot of storage devices.

You can have materials that are super strong okay, and again…again these are solid state

materials, where for some reason or the other the properties are…are unexpectedly good

okay.

Then, there are these almost magical materials that are there again…again these are solid

state materials.

These are just to give an example there is this whole class of materials called meta

materials, which have negative transport properties.

So, for example, they can have negative temperature coefficient of resistance or they can have

negative refractive index.

So, there is a whole and these are not….these are not single compounds, but these are actually

materials, where you where you do various things I mean you put one layer of one material

another layer of a different material and you and by you know manipulating the entire

material okay, you make these almost magical materials.

And, another example again…..again this is in the same class as meta materials okay,

I am calling it a win-all material, which typically has more than one property that

is very good.

For example, you can imagine that you have something that is both super strong and super

light, okay.

So, that would be a material that has….that is both super strong and super light, which

is not typically found.

So, so, these are typically nanocomposites are used to really tune multiple properties.

There are again graded materials, where you have different materials in different proportions.

Many of these win-all materials are biocompatible they are environmental friendly.

So, usually when you take a solid state material you say that oh it is…it is not going to

be biocompatible, but by manipulating them you can generate these….these exceptional

materials, which are both biocompatible and environment friendly.

So, I will conclude this lecture here for today.

So, what I have tried to show in this lecture is…is the basic properties of the solid

state of matter and what are the general framework, in which we try to….try to understand and

study the solid state of matter.

Thank you.