I have made two mistakes in this video 😞: 1. I have considered Trigonal and Rhombohedral as synonyms for the same crystal system. However, as per the International Tables of Crystallography Vol A it.iucr.org/A/ the two terms are NOT synonymous. Crystal System should only be called Trigonal and not Rhombohedral. 2. I have shown only one Bravais lattice in the trigonal crystal system. But in reality there are two Bravais lattices in the trigonal system: hexagonal prinmitive (hP) and hexagonal rhombohedral (hR). And so there is no trigonal P Bravais lattice as shown in the table in this video. I plan to make a video to clarify this. Wil share the link once I do it. You can check en.wikipedia.org/wiki/Crystal_system.
@one.darkstar Жыл бұрын
Thank you, sir. We will note that. You are awesome.
@Summer693843 ай бұрын
Hats off to his dedication ❤
@andersonalvarado72784 жыл бұрын
espectacular, estoy muy agradecido por esa información compartida. Mucho respeto y agradecimiento para el profesor Rajesh Prasad e igualmente para el Instituto de tecnología Delhi y el NPTEL. Gracias :)
@melvindavis36296 жыл бұрын
I wish i could have a professor like you when i was doing B.E
@rifqihammami39353 жыл бұрын
I like with his explanation. Everything is easy to understand. Keep it up, Sir and don't be bored to share knowledge. May God bless you always. Aamiin ...
@unmeshlondhe24975 жыл бұрын
Sir you are simply great... The way you are teaching is amazing... Thanks for your vedio lectures..
@swastikdeshmukh4065 жыл бұрын
Stunning teaching art sir thanks a lot
@preetishsajwan45026 жыл бұрын
By far the best explanation of this topic on this platform.
@jaswanthkumar81573 жыл бұрын
Even at end of lectures your making it so interesting sir
@makhmulshaikh86706 жыл бұрын
Sir I am enjoying this sessions..nd feeling like in college lecture... Thank you very much
@ThePabler64 жыл бұрын
Me too
@akashdeep50883 жыл бұрын
Describing you in a word " Legends"
@sirbaggy4 жыл бұрын
Really interesting and well presented series of lectures.
@a.kanagavalliponvetrivel22714 жыл бұрын
excellent explanation sir. thank you sir
@bg73635 жыл бұрын
Its pleasuring to learn with your video...
@natashawhite7124 жыл бұрын
i respect you so much professor.
@sci-fi19984 жыл бұрын
Sir,Thank you for your nice lecturure.. And i am requesting you to make a video for crystallization magma..unicompoments, bicomponent and ternary.. How to calculate those percentages of component
@sameerkhan-fw2lq5 жыл бұрын
Excellent explanation 👌
@KajalKumari-nk3wl4 жыл бұрын
Good explanation
@truescienceknowledge5 жыл бұрын
Sir please explain what is 1) cubic 2) tetragonal 3) orthorhombic 4) hexagonal 5)trigonal or rhombohedrical 6) monoclinic 7) triclinic
@jaswanthkumar81573 жыл бұрын
Thank you sir, the finest lectures I heard on MMS subject. Sir,could you please suggest me the reference books of your lecture.
@blzKrg3 жыл бұрын
Try Charles kittel or Physics of materials by Prathap Haridoss.
@jaswanthkumar81573 жыл бұрын
Thank you sir for your suggestion
@sayanjitb3 жыл бұрын
Ashcroft mermin ... You can try it
@jaswanthkumar81573 жыл бұрын
@@sayanjitb 🙏thank you sir
@paulboro52783 жыл бұрын
Sir, some books also consider unit cells which do not have lattice points on the corners, which is very confusing to me.
@introductiontomaterialsscience3 жыл бұрын
It is possible to choose unit cell where corners are not lattice points. All that is required is that the corners should be translationally equivalent points. Thus if you begin with a unit cell with corners at the lattice point and shift it parallel to itself by a non-lattice translation then you will get a unit cell whose corners are not lattice points. I avoided this complication in my video as it is simpler to choose a unit cell with corners at the lattice point. I would like to see the specific example which you came across in the book you studied.
@blzKrg3 жыл бұрын
Urgent question! What exactly does it mean to say "crystal system?" Are we classifying crystals or unit cells? Some books say there are 7 types of unit cells and some others say there are 7 types of crystal systems and i can't figure out the difference.
@rajeshprasadlectures3 жыл бұрын
We are classifying crystals based on whether they possess certain characteristic rotational and reflection symmetry. Thus if the crystal has four three-fold axes it will be said to belong to the cubic crystal system. If the crystal has this symmetry it is also possible to select a conventional unit cell in the shape of a cube. The definition of the crystal system should be based on symmetry and not unit cell shape. There are two reasons for this: 1. If the crystal has cubic symmetry, then as stated above, a conventional unit cell in the shape of a cube can always be selected. One can also select a different unit cell that is not cubic. Even if we select a non cubic unit cell the crystal system remains cubic because of it symmetry. We are concerned with the symmetry of the entire crystal and not a particular unit cell. An interesting example is a selection of a primitive rhombohedral unit cell in an FCC lattice: kzbin.info/www/bejne/aZDHqmucrMR0rZY 2. Reverse is also possible. Sometimes, accidentally one may select a unit cell that is cubic in shape but the crystal does not have the cubic symmetry. An example is provided by a base-centered (or end-centered cubic) lattice. Despite the cubic unit cell the lattice produced does not have cubic symmetry. So the crystal system is not cubic but tetragonal.kzbin.info/www/bejne/h6ubgpWIismCbtU Thus in summary, 7 crystal systems are classification of crystals on the basis of symmetry and not unit cell shapes.
@blzKrg3 жыл бұрын
@@rajeshprasadlectures thank you so much professor! I've been confused about this topic for really long.
@sayantanbhattacharya87945 жыл бұрын
Sir,I am searching for an answer that why are there only 7 crystal systems ?
@rajeshprasad1015 жыл бұрын
A difficult question to answer.
@pranitudanshive51214 жыл бұрын
Mathematically, in 3-D ,we cannot have any other periodic arrangement of atoms or molecules different than these 7 crystal systems.
@alijutt36755 жыл бұрын
Amazing way of teaching. Well, I have a question, crystal system is basically a method of classifying a crystalline substance on the basis of its unit cell. so when we say we have 7 crystal systems, does it mean we have only 7 types of unit cell periodicity? and in the previous video, you told that we may have infinity unit cells.
@rajeshprasad1015 жыл бұрын
7 crystal systems are not seven kind of unit cells, although that is how it is usually presented. It seven different types of rotational/reflection symmetry which a lattice can have.
@blzKrg3 жыл бұрын
Yes, we can have infinite unit cells in a lattice, however in this video he uses the word "conventional" unit cell as in the unit cell that is most appropriate.
@akshayzade31535 жыл бұрын
At 19:00 in lecture, rather than considering all edge centered in Simple cubic, if we consider only 1 set of parallel faces as edge centered then is that lattice structure possible ? Also as its possible that length of unit cell can vary in all three directions a,b,c. We can say, Its not compulsory to get another lattice point by traveling same distance like you did in lecture at 19:00, please explain..
@rajeshprasad1015 жыл бұрын
Is it possible for you to draw a figure?
@aashrithyellambhatla63313 жыл бұрын
Sir, in proving that an edge centered lattice is not possible ,the reason which you have given is not quite convincing for me because if I take a bcc lattice then according to your explanation the corner lattice points and the center lattice point are not equivalent even though we are saying this lattice is possible. Can you please explain it for me sir?
@introductiontomaterialsscience3 жыл бұрын
In BCC the lattice point is at the centre of the cube. This is allowed. What is not allowed are lattice points at the centre of the edges of the cube.
@blzKrg3 жыл бұрын
All points in the corner are at the same distance from the body center point so it doesn't violate the definition of a lattice.
@Upgradezz3 жыл бұрын
The real issue is why only 7 crystal system and why only 14 bravais lattices
@BC-yr6eg4 жыл бұрын
👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻
@amanbhati84654 жыл бұрын
Rajesh sir moj kaar de
@sahilgajbhiye06563 жыл бұрын
ty very much sir
@saritasatua32672 жыл бұрын
Thanku sir
@muzammilhussain98053 жыл бұрын
Ty sir
@serialscindy6 жыл бұрын
What steps are required to mathematically prove that there are only 7 crystal systems?
@rajeshprasad1015 жыл бұрын
You have asked a hard question. This is something I have not yet figured out!
@Upgradezz3 жыл бұрын
@@rajeshprasad101 really?
@introductiontomaterialsscience3 жыл бұрын
@@VijendraSingh-hc5ky I think what you say has some truth in it in the sense that classification into 7 system is not totally mathematical but there is an element of convention in it. There are 32 point groups of crystals. This is a purely mathematical result. But the classification of these point groups into crystal systems involves some arbitrary convention.
@cokedupnormies26515 жыл бұрын
Can a unit cell be triangular?
@rajeshprasad1015 жыл бұрын
In our definition of unit cell it should be a region which can tile the space by translations. Triangle cannot do it by translations. So we cannot select a triangle as a unit cell.
@staycalmandgetsuccess87434 жыл бұрын
@@rajeshprasad101 sir please explain simply . I am not getting the answer. I think triangular lattice is possible but triangular crystal is not possible.correct me if i am wrong
@staycalmandgetsuccess87434 жыл бұрын
@@rajeshprasad101 is this 7 systems are derived or we have found that practically?
@blzKrg3 жыл бұрын
@@staycalmandgetsuccess8743 triangular lattice might be possible but triangular unit cell isn't possible because a unit cell has to tile all of space by only "translations" but we need to rotate a triangle to make a lattice. Try it at home by making a simple lattice and trying to cover all of it by just translating a triangle.