Crystal Definition and 430 Threads

I've learned that in a crystal, the crystal momentum is conserved. When one considers the electrons as Bloch waves, they have a momentum that doesn't commute with the Hamiltonian and they have well definite energies, hence they cannot have a well definite momentum, because there is no basis in...

I need to make my own smart film for some experiments. I've read enough articles on it to know the required components, how they are mixed and applied. I have a 1:1 mixture of liquid crystal and UV curable resin and glass bead spacers that I need to apply between two ITO PETs and UV cure to...

Homework Statement Consider the crystal in the attached image (https://ibb.co/ftMrBH) (a triangular lattice of white atoms with a triangular basis of grey atoms attached to them at angles of 0, 60 and 120. From a previous problem the fractional coordinates of the atoms in the basis are (0,0)...

I am able to find methods on how to index Bragg peaks for powder diffraction, and was wondering if the method is the same for single cubic crystals of NaCl? I have tried and cannot get the expected sequence of allowed reflections for cubic lattices (h^2 + k^2 + l^2= 3, 4, 8, 11, 12, 16, 19...

I need help regarding piezolectric effect... If I add DC voltage to piezoelectric crystal it will change its dimension (length) and vice versa: if I put pressure on piezoelectric crystal it willl produce DC voltage on its surfaces... But I am wondering how long this voltage will last? If I keep...

Hey guys, can't seem to make sense of this question from phys. It goes.. "A crystalline solid consists of atoms stacked up in a repeating lattice structure. Consider a crystal as shown in Figure a. The atoms reside at the corners of cubes of side L = 0.200 nm. One piece of evidence for the...

Hey, The question sounds like this: I have 100 fs 400 nm pulse passing through the CaF2 crystal. After passing, it gets twice wider (200 ps). What is the length of the crystal? Can anyone share the equation which would help me to calculate this? Thank you in advance!

Is it theoretically possible to cool a macroscopic crystal (for example NaCl 1×1×1 cm) to an extremely low temperature, like 1 nK? Will it retain its microscopic structure? Why? Does it have anything to do with zero point energy (I mean something like the lowest energy level of a quantum...

Say that I have a neodymium doped yttrium aluminum Garnet (Nd:YAG) laser crystal rod. If I'm using this crystal in a laser, will the size of the crystal affect any characteristics of the laser itself. That is, will a laser containing a 4-by-7 mm Nd:YAG rod operate differently than a laser...

I would imagine that it doesn't. I'm really sure how to rationalize this. If emission is a decay process, I don't think the rate constant would change with concentration, and likewise crystal size. Any spectroscopist out there?

Homework Statement Find the magnetic moment of a crystal when placed (i) in a weak field at high temperature (ii) in a strong field at low temperature Homework Equations This is the last part of a question which I feel I have solved correctly up until this point. The mean magnetic moment I...

I have stumbled upon an interesting article in wikipedia: https://en.wikipedia.org/wiki/Time_crystal While i somewhat understand the concept, i was unable to find applications or at least repercussions of said crystals. I am not of QP background, so even if its obvious, could someone be kind...

Hi, I am having trouble wrapping my head around a simple (I think?) question about birefringent walkoff: If the crystal is oriented at some angle such that walkoff is nonzero between e and o beams (in a nonlinear conversion process, for example), it seems to me that reflecting the light...

we have heard that pyramids, old temples are made from hard stones containing quartz crystals. Is they radiate any kind of energy so that we get a pleasant feeling?

This picture appeared on the welcome page when windows10 was powering up this am . I found this further information : http://unusualplaces.org/the-crystal-mill/

Hi everyone, to find the draw the direction for a given miller index say, [1234] we first convert this miller index consisting of 4 indices into one containing 3 indices. To do so, we have a set of formulae prescribed in almost every book. Sadly I haven't been able to come across a single book...

I was studying about Crystal defects in crystals and came to know that it has huge effect on band diagram.I don't know about their specific impact on band diagram.So what are major impacts of crystal defects on band diagram.?

Homework Statement The problem from Sterway, Jewett book. The Attempt at a Solution The answer in the book is something like 0,141 nm, as I remembered but I cannot achieve such answer coz' I cannot understand what actually asking, d is looks like a distance between two centers of the...

Are a strained crystal still crystal? How to prove it? Are the unit cells of the strained crystal still the periodic elementary building blocks of the transformed crystal? Does the transformed crystal own the same volume as that of the perfect crystal? Can we treat the strained crystal as the...

For the crystal lattices and structure Question picture is uploaded. Question.jpg My attempted answer is uploaded by a picture. My attempted ans. 1.jpg My attempted ans. 2.jpgThere is any mistake?

Homework Statement Homework Equations I'm not sure. The Attempt at a Solution I started on (i) -- this is where I've gotten so far. I am asked to compute the Fourier transform of a periodic potential, ##V(x)=\beta \cos(\frac{2\pi x}{a})## such that...

Can someone explain this paragraph especially the bold part in simpler language: "If it is not in a major crystal direction or plane ("random direction", Fig. 2), it is much more likely to undergo large-angle scattering and hence its final mean penetration depth is likely to be shorter." full...

This question is as dumb and simple as it can be: Why is the path difference 2dsinθ? Or better said: Why x-ray scatters like in the image? (Couldn't there be another scattering angle for both atoms other than θ?)

How does the load capacitance affect the Crystal. For example, IC manufacturers recommend a Crystal and also load capacitance, like 25MHZ, 16pF. What happens if I choose a xtal with load cap of 10pF 25MHz? I am talking about changing the load caps recommended by IC manufacturer, not the ones in...

Hello, Sorry if this is a rather basic question, but my memories of solid-state chemistry are a bit rusty. Basically I'm trying to predict new crystal structures. I understand the crystallographic aspects quite well and know that at given external temperature and pressure the most stable...

I was reading this interesting article at Wikipedia about recent work by Nobel laureate and professor at MIT Frank Wilczek in 2012: https://en.wikipedia.org/wiki/Space-time_crystal It sounds like some scientists are close to actually making some of these crystals: Could you please explain to...

Homework Statement The conduction band of a hypothetical crystal of one-dimensional Cesium reticular with step a=300 pm (1 atom per cell) is characterized by the ε dispersion law ##\epsilon (k) = V_0 + \frac{\hbar^2}{m_e}(\frac{1}{2}k^2 - \frac{a}{3\pi}|k|^3## where ##V_0 = -4 eV##, is set so...

Why in most practical applications, most materials properties are given without specifying crystal directions. Are they trying to say all materials are isotropic?

There are some types of crystals we call them XY type (i.e. NaCl) or X2YZ type? Could XY type be a special case of X2YZ type by assigning Y=Z?

I'm no physicist, but I found this material to be interesting. Samarium Hexaboride is a crystal that exhibits conductive properties at room temperature and insulating properties when cooled to below minus 223 degrees Celsius. A layman's article...

There are some software can provide visualization of crystal or protein structure, i.e. VESTA. I want to know how many atoms is the nearest neightbour (and their distance), and the next nearest neighbour...etc of a particular atom. Is there any software (or perhaps some data book?) can do this?

I would like to find the crystal structure of (Pb0.5Sn0.5)Te I was told it is similar to NaCl basically an XY crystal I think it is called Space Group: 225 I would like to know the first, second, third ...layer of atoms closest to a X atom...and perhaps their distance... I found...

Hello, I am stuck at the beginning of an exercise because I have some trouble to understand how are the energy level in this problem : In a crystal we have Ni2+ ions that we consider independent and they are submitted to an axial symmetry potential. Each ion acts as a free spin S=1. We have the...

What are some good resources : books, websites, etc to understand crystal optics? I am a graduate student and I want to start with the basics.

Hey guys! I come back to solve a new problem with your help! 1. Homework Statement Use the Lennard-Jones function: $$ V(R)=4\epsilon[(\frac{\sigma}{R})^{12}- (\frac{\sigma}{R})^6] $$ like as a adiabatic potential energy model in function of separetion R between cople of argon nuclei. With ##...

If I shine a laser beam through a calcite crystal, the beam is split in two, as shown below. Are the photons in the split beams in an entangled state?

I know what the definition is, but the concept it's conjuring for me seems in my experience of learning about these things, to indicate that I'm missing the point completely. What does it mean for something to be oscillating when it's in a ground state? I was under the impression that such a...

Hello, I'm trying to better understand the limiting factors in Diamond Anvil Cells that limit the achievable pressure to around 7 or 8 Mbar at the moment, despite not being a specialist. For example, is there a special reason other than the tiny size of the crystal sample used in DACs for why...

Im supposed to make model to demonstrate all-optical switching using a nonlinear effects of photonic crystals. And I will be using a directional coupler for this purpose. However I am having trouble in understanding the theory and concepts related to coupling / coupling length / use of...

Hello, I was building some test crystal structures with VESTA software and I noticed when generating the POSCAR output files to be read by VASP that for a simple monoatomic basis such as in elemental silicon crystals some distinct space groups produce the same exact POSCAR files (i.e. same...

Let's say that I deform some piezoelectric tile and the energy(Fs here) is stored in form of some stress energy and some electrical energy(distribution of the centres of charges looking as a capacitor). Now I remove the force and then remove the electrical energy somehow so by the inverse piezo...

I was bored today so I took this diamond shaped crystal made of glas and simply put in infront of the light emitting from the sun. What I noticed was a lot of lines on the wall that were strangely colored, just like the electromagnetic spectrum. One end was blue, then progressively went to red...

Hi all, I’m brushing up my skills on solid state physics and I have a few questions about crystal lattices: 1. What’s the spacing between allowed kx, ky, and kz states for a lattice of dimensions La x Lb x Lc? My attempt: The spacing is kx, ky, and kz: k_x = \frac{2\pi}{L_a}, \qquad k_y =...

In a crystal, the index of refraction is always calculated in the Lorentz oscillator model by examining the electronic response to an incident field and assuming a stationary nucleus. Is there however, any contribution to the index from the ionic nuclei in the background? I assume since I've...

Homework Statement Silicon crystalises in a cubic structure whose lattice is face-centred, with a basis [000],[1/4,1/4,1/4]. How many optic/acoustic modes are to be found in the phonon dispersion diagram for silicon. How many distinct branches would you expect along the [100] direction...

I find in many textbooks that when expanding the crystal field in spherical harmonics, those terms of odd ranks do not appear in the expansion even if the crystal lacks an inversion centre such as the tetrahedral crystal field. Why is that? and when one should include spherical harmonics of odd...

Hi! The crystal that I am growing is Mohr's salt. though i have already optimized the parameters (pH), i would like to know the reason why pH affects it's growth. pH 1: no crystals formed pH 2: crystals formed Thanks!

What determines the crystal structure taken by metals? For example Sr has FCC and Ba BCC. The packing fraction is greater for FCC. However, due apparently to coordination number and number of "next nearest" neighbors, BCC is favored in the case of Barium despite its lower packing fraction...

Is it correct that a crystall of simple lattice (lattice with primitive cells each having only one atom) cannot be antiferromagnetic? In other words, the antiparallelism must occur between atoms within each primitive cell. Thanks.

Does a type I superconductor has to be single crystal? If not, is there any change in its Tc when it becomes polycrystal? Thanks.