RECIPROCAL LATTICE

Transcript

hello everyone welcome again to your own channel theoretical contest matter physics and here we are with a very important and fundamental concept of contest matter physics the reciprocal ltis and actually I can quite bet that you have gone through this particular topic various times through textbook references and probably few videos also but somehow absolute clarity about this particular topic it's still missing within you right however let me assure you if you can just give me five minutes of your time you won't have to go through any other video or study material about this conceptualization of reciprocal ltis okay okay let's begin let's say you are driving a car along a straight road and encountering one lamp post at each 100 m however one other way of defining this phenomena is also that you are encountering 10 lamp posts for each kilometer right and then the unit of that particular quantity which you are measuring will be kilometer inverse that is 10 lamp poost for each kilometer now clearly if the spacing between the lamp poost decreases definitely the quantity that we are measuring that is the number of lamp poost by each kilometer will increase right I hope up to that point no confusion is there and of course I was not talking about the lamp post and the curve you can map actually the lamp post directly to the periodic arop atoms and the car this actually symbolizes the light to be specific the X-ray that is actually what is passing through that periodic array or in other words the crystal now a similar kind of thing happens to that passing light the very famous BR defraction and as you know from the law of bra defraction two 2 D sin Theta is equals to n Lambda or sin Theta is inversely proportional to D or in other words the angular separation Theta between the Maxima is inversely proportional to D which is the interatomic spacing between the crystals now from the law itself one thing is very clear that with the increase of interatomic spacing the distance between the two Maxima decreases or in other words if you are considering a screen of fixed width then the number of Maxima within the screen will actually increase and hence for defraction we get more number of Maxima within the screen right now let's try to understand what is this 1 by D if we have a tonal litis and we are considering X Direction only then definitely D will be the latis parameter a right so the deflection pattern will directly Rel to that 1 by a or more technically speaking B Cross C that is the area in y z plane divided by a b Cross C by volume so that will be actually 1 by a right therefore a clear understanding of the reciprocal ltis vectors is very useful in the study of defraction and if you remove the constant weight is the deflection pattern is actually a clear visualization of the reciprocal ltis now let me give you some more information about that if you add some impurity to that crystal structure the deflection pattern will still remain the same while the intensity of some of the Maxima may vary now another thing that you should know in this context is even if you are measuring something amorus which does not actually have a crystal structure then also the examination of the deflection pattern can provide some very useful data like the average distance between the atoms and molecules of that matter right however so that was it and I hope no further question about reciprocal latis is there and still if you are having some doubt definitely you can just comment here in the comment box and thank you thank you all uh okay let's meet again in the next video and till then like share and subscribe thank you thank you all thank you