Thank you sir very much you are a great teacher and helped me in my MLL100 course at IIT D .

Sir, thank you so much for delivering your lectures in such passion. These lectures should be shared for teachers training in Indian universities. Got goosebumps all along. Thank you once again sir. Also for any student reading this comment, I need to mention with utmost delight the comment section is equally resourceful. 🙏

Sir, can you please tell about no. of second nearest neighbours and their distance in hcp crystal?

Sir while calculating packing effeciancy what should I consider hexagonal prism or rhombus prism?

@introductiontomaterialsscience

3 жыл бұрын

You can use either. Both will give the same result.

the ideal C /N ratio for the hexagonal close packing the radius of largest sphere that fitted in Titanium sir please solve, (a=2.7A)

Hi sir... Does a greater C/A ratio means that ionic bond is not strong in Zn and Cd

@introductiontomaterialsscience

4 жыл бұрын

The bond in Zn and Cd is not ionic but metallic. Larger c/a does mean that interplanar bonding between basal planes should be weaker.

Respected sir, will this ratio effect slip systems because we know most widely spaced planes are the slip planes and if this ratio is decreasing that means, a increasing or c decreasing?

@introductiontomaterialsscience

3 жыл бұрын

The point you have raised is interesting but it is not really the case. HCP metals mostly glide on basal plane {0001} in the close-packed directions . But in some cases prism planes {10-10} are also observed with the same slip direction. However, this variation is not related to the variation of the c/a ratio. This is because c/a ratio is only a geometrical factor. Slip is a physical process which also depends upon interatomic bonding in the crystal. I am basing my answer on the book Crystallography and Crystal Defects by Kelly and Knowles (earlier editions Kelly and Groves and Kelly Groves and Kidd) which you can check for more details.

@kommulasatwik8421

3 жыл бұрын

Thank you sir.

Sir but the base in hexagonal lattice is having the basal plane of regular hexagon... But here we have rhombus .. please clarify ... Getting confused

@introductiontomaterialsscience

4 жыл бұрын

Two kinds of unit cells are popular with HCP crystals: hexagonal prism and rhombic prism. The rhombic prism is a primitive unit cell with rhombus of side 'a' as the base. This has one lattice point and two atoms per unit cell. The hexagonal prism has a regular hexagon of side 'a' as its base. This has three times the volume of the rhombic primitive unit cell (the hexagon can be divided into three congruent rhombi). Thus it has 3 lattice points and 6 atoms per unit cell. The rhombic prism has the advantage that it is primitive and small. But it does not make the hexagonal symmetry obvious. The hexagonal prism is large but shows the hexagonal symmetry. The hexagonal Bravais lattice is called Hexagonal P or Primitive Hexagonal. Thus strictly speaking the primitive unit cell should be considered the conventional unit cell. The non-primitive unit cell is a non-conventional unit cell. Once you understand the relationship between the two unit cells there should be no confusion in using either.

@amritjena3210

4 жыл бұрын

@@introductiontomaterialsscience thank you sir ... I am using this lockdown days for preparation of gate 2021 .. your lectures are really good to brush up my clarity of understanding..🙏

@ricky5369

3 жыл бұрын

@@introductiontomaterialsscience once I saw it, it blew my mind. I had the same question.

@rajendra prasad Sir how many atoms are present in a HCP unit cell And are these different from the No of atoms in a HCP crystal

@introductiontomaterialsscience

Жыл бұрын

In the primitive HCP unit cell there are two atoms: 000 and 1/3 2/3 1/2. The no. of atoms in an HCP crystal is not a well-posed question, as crystal is infinite.

Sir, why c/a ratio varies with the type of chemical element, like Zn and Cd. Could you please give clarity?

@introductiontomaterialsscience

2 жыл бұрын

It is indeed a very interesting question. But I do not know the answer. And I guess the answer is not known, but I may be wrong.

@saurav1916

2 жыл бұрын

@@introductiontomaterialsscience does this mean that atoms are not touching (for c/a > 1.633) and therefore packing fraction should also be less than 74%

@introductiontomaterialsscience

2 жыл бұрын

@@saurav1916 That is right.

How it is possible to determine the c/a ratio of an element? Is it the crystal containing those elements?

@rajeshprasadlectures

3 жыл бұрын

Both c and a can be measured using x-ray diffraction. I could not understand your second question. Could you please explain?

@Asasmal

3 жыл бұрын

Sure sir, (if i heard it right) you have said C/A ratio of an element. I think C/A ratio is valid for crystal not an element.

@rajeshprasadlectures

3 жыл бұрын

@@Asasmal c/a ratio is used here for HCP crystal. There are many elements that have an approximate HCP crystal structure like Mg and Ti.

Should work out the problem

Sir could you please explain how this c/a ratios are worked out for real elements? How the displacement vectors /distances are measured? Kindly explain.

@introductiontomaterialsscience

4 жыл бұрын

This is done by x-ray diffraction.

How to calculate height of tetrahedron: kzread.info/dash/bejne/m6p6ldCdnc6zo6g.html