Sir your teaching is excellent get knowledge in subject.y u can take some other branch in physics like modern physics,electrostatics,etc i saw u r teaching in crystal growth .u r teaching is very good .
Again Awesome explanation. But, quasi-crystals can occur with 5-fold symmetries; these were not discovered until 1982 by Dan Shechtman. He won Nobel Prize for discovering quasi-crystals in 2011.
Sir, does these n values have anything to do with shape of unit cell?? i mean does this mean that a pentagon unit cell is not possible as it does not possess symmetry, and unit cell of other shape are possible?? thank you .
Well, n=1 can be considered zero of symmetry. Rather than saying that an object has no rotational symmetry you can say that it has n=1 rotational symmetry.
Sir, you said we will not prove why crystallographic restrictions have only 5 types of rotational axis... So you mean mathematically there is a proof for this?
@@introductiontomaterialsscience indeed I googled it sir. Fascinating. Although from the outside an atom looks like a physical concept but at the same time how mathematical can it be.. just mind-blowing..
Sir in rotation symmetry, the motion or translation is about the axis.... I couldn't get translation in reflection and inversion symmetry and also how is it different from the rotational. Can someone please explain this to me.
Just like rotation is about an axis, reflection is about a plane and inversion is through a point. Rotation is a physically possible motion. Reflection and inversion are only possible in imagination. Is that what is trobling you?
@@introductiontomaterialsscience I understood what you mean now.. thank you for taking the time to reply... I have seen almost the entire course multiple times... this course is slowly becoming like the Mahabharata Epic. I watch again and again and new meanings evolve. thank you, sir....
1-fold means no rotational symmetry. It is possible to have a crystal with only translational symmetry and no rotational symmetry. Therefore, 1-fold is allowed for crystals.
