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11 views

What are some structures which minimize surface stress upon expansion

Intro I am currently researching into a problem involving the cyclical expansion and contraction of a 3 layered structure comprised of an internal metal encased by another metal encased in an outer ...
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0answers
23 views

How many atoms in the particle (AuNP) [on hold]

Let's say I have to determine number of atoms of gold in ball-shaped nanoparticle with diameter of 75 nm. I need general method of solving such problems more than specific answer for only this ...
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1answer
136 views

Do indirect optical transitions “cool” the material a little?

So I'm reading in Ashcroft and Mermin about indirect optical transitions: So, a photon comes in, and it only excites the electron across the indirect band gap if a phonon with the appropriate wave ...
3
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1answer
33 views

Lattice geometry and dispersion relation

Is there a general theorem which gives some information about which influence have the lattice geometry (for example sub-lattice structure, square lattice, honeycomb lattice, lattice symmetries, ...) ...
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1answer
21 views

Effect of crystal growth on its scintillation

How does crystal growth affect its scintillation properties? What are possible ways in which growth of CaWO crystals grown via Chochralski method could be modified to avoid non-linearity in its ...
4
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1answer
278 views

What is crystal field anisotropy or effect ? It forces the magnetic moment to point in particular local direction..

Can you give a basic explanation of what is crystal field anisotropy ? What is the reason to arise ? In spin ice it forces the dipoles to point in the local 111 direction. For partially filled rare ...
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2answers
5k views

Why does ice have a lower density than water?

Can someone explain me why is ice lighter than water? As I know, all solids are usually heavier than the liquids (correct me if I am wrong).
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1answer
50 views

How can one reasonably theoretically model polycrystalline materials?

Many techniques are taught in advanced solid state courses but they are almost all derived for perfectly crystalline materials. For example, band structure really only appears theoretically when you ...
2
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1answer
92 views

Kronig-Penney model

I am studying the Kronig-Penney model as treated in the book by Kittel: Introduction to Solid State Physics. In this model one considers a period potential which is zero in the region $[0,a]$ ...
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1answer
59 views

Reciprocal Lattice of a non-bravais lattice

Is a reciprocal lattice defined for non-Bravais lattices? I'm trying to work out one for HCP structure and not figuring it out.
2
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2answers
70 views

Quantity to measure order in crystals

Imagine a cubic lattice for simplicity and put some atomic configuration inside of each unit cell. Lattice is of course a highly ordered entity (long range order). Please, how could I quantitatively ...
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1answer
70 views

Why can't a dislocation terminate in the bulk?

We are told that they can only terminate on surfaces, grain boundaries or other dislocations but we are not told why they can't terminate inside the crystal.
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2answers
37 views

What exactly are crystal planes and how do they reflect x-rays?

What exactly are crystal planes and how do they reflect x-rays? Are crystal planes real physical planes or just an abstract concept? What are these planes made of? If they are an abstraction, what ...
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1answer
42 views

Are there any electro-optic crystals that are also pyroelectric but not birefringent?

As the title says, a crystal that is electr-optic and pyroelectric can it be non-birefrigent?
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1answer
93 views

Crystal Momentum in a Periodic Potential

I'm working through some basic theory on periodic potentials, and I would appreciate help in understanding the crystal momentum. Suppose we have a Bravais lattice with lattice vectors $\textbf{R}$. ...
3
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1answer
43 views

What physical phenomenon occured in this experiment?

I noticed a strange behavior of my experiment. I have a glass container with a fully saturated solution of CuSO4, which I use to grow CuSO4 crystals, by waiting for the water to evaporate. Recently I ...
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0answers
27 views

Mixed-Alloy materials

Short version: Is it a physical problem (crystal structure/grains/redox/etc.) or just a logistics problem (keeping the solutes from homogenizing, molten/solid/temperature related problems) that keeps ...
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0answers
16 views

3-dimensional quasicrystals

As is well known, quasicrystals (i.e. their diffraction patterns) show patterns which can be deciphered and understood via the use Penrose tilings (and aperiodic tilings of the plane in general). ...
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2answers
88 views

Bloch theorem, Energy, Free electron

I'm trying to learn on my own a bit of solid physics to tackle semiconductors afterwards. I'm struggling with the Energy versus $k$ diagrams for a free electron which shows that for a single value of ...
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0answers
69 views

Why is there a 'loophole' in Mermin Wagner for rotations?

I'm just starting out in my mathematics career by looking at some simple stuff on broken symmetries in statistical mechanics. Since 3D is 'hard' it would be very nice to look at 2D toy models of ...
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2answers
161 views

Bloch's theorem

I am studying Bloch's theorem, which can be stated as follows: The eigenfunctions of the wave equation for a period potential are the product of a plane wave $e^{ik \cdot r}$ times a modulation ...
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4answers
294 views

How many of the 230 crystallographic groups are realized in nature?

All of them or only a subset? This is a famous and fundamental result in solid state physics.
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3answers
19 views

How to calculate the density of a polycrystalline sample?

I'm trying to figure out the density (g/cm^3) of La2CuO4. I know that the mass is 405.355 g/mol; what do I have to do to calculate the volume? Thanks!
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2answers
114 views

Simplest derivation of Fourier transform for periodic functions (in crystal lattice)?

What is the simplest derivation of the following two well-known formulas that work for crystal lattice [1]: $$ F[f(\mathbf{x})] \equiv \tilde f(\mathbf{G}) = {1\over\Omega_\mathrm{cell}} ...
3
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1answer
27 views

Why do we still get sharp scattering spots with quasi-crystal?

In a quasi-crystal, there is no translational invariance. This means there is no delta-function in the Fourier transform. But to get a sharp scattering spot, we need a delta function. Physically, ...
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3answers
112 views

Should a polyatomic crystal behave similarly to the bulk of each/either of its constituent elements?

Generally, metals are usually fairly conductive, but their oxides aren't. I know conductivity is just one attribute, but in general, should you expect a, say, diatomic bulk crystal's properties to be ...
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2answers
159 views

How strong is electron degeneracy pressure?

I'm trying to get some specific numbers for electron degeneracy that I can understand, using a concrete example. Take for example this portion of carbon crystal: Exactly how much energy would be ...
0
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1answer
39 views

What is the symmetry difference between simple-cube and body-centered-cube structures

If the lattice types are categorized according to the point group symmetries, then what is the difference, for example, between sc and bcc structures?
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2answers
112 views

Are there materials that get softer with temperature decrease?

Could be there material that begins melting/softening when it's temperature is lowered? I would say no, but I've seen enough physics to know that not always life is so easy. Moreover I think I've ...
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1answer
149 views

Ashcroft Mermin Solid State Eq. 22.15

I recently read a paper on Specific heat of a Classical Crystal: Dulong-Petit law. In Eq. 22.15, I don't understand why the ionic displacement $\mathbf{u}$ and ...
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0answers
37 views

Which metal will be on the surface after solidification?

I know that there are some metals that just "like" to be on a surface, so if I make an alloy of such metal and some other metal, the first one will be on the surface after solidification of initially ...
2
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1answer
41 views

Why does a halocline form?

I was doing an experiment over the last couple of days to try to crystallize alum using a thermal gradient. The idea was that solute at the bottom of my container would be dissolved at a higher ...
4
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1answer
175 views

Origin of Laue equations?

The Bragg condition (by Bragg in 1913) can be derived by the Laue equations that is making use of the Miller indices and all the latice/crystal stuff (so basically it's bringing Bragg's law to more ...
0
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1answer
115 views

Why a mono-atomic crystal layer (2D) can't be stable?

According to Peierls and Landau, 2D crystals were thermodynamically unstable. They can't exist! Of course, this theory was disapproved in 2004 (example: graphene). What is the general definition of ...
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0answers
65 views

Pseudocubic unit cells: how to construct one?

I keep coming across the term pseudocubic unit cell while reading about orthorhombic perovskite structures. No clear explanation ...
2
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1answer
99 views

What does (001) Silicon mean?

If someone gives me a thin film of Si, and they tell me it's (001) Si, does that mean that the (001) planes of Si are the ones making up the surface of the film?
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38 views

How can I get the lattice constant of a salt?

This is probably a very dummy question, but I am not able to solve it on my own. Given that the radius of $Li^+$ ions is 76 picometers, and the radius of $F^-$ is 133 pm, I would expect the size of a ...
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0answers
25 views

Transmissivity of Liquid Crystals in the near-infrared range

The gist of my query is in the title. I have been searching for papers and studies that could provide transmission curves (in nematic liquid crystals) across the visible to near-IR range (or from ...
0
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1answer
53 views

Translation invariance in crystals

Context: solid state physics - dynamics of atoms in crystals. Coupling constants are defined as: \begin{align*} \frac{\partial^2\Phi}{\partial r_{nai}\partial r_{mbj}} = \Phi_{nai}^{mbj} ...
3
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1answer
110 views

Difference in chemical potential in supersaturated solutions

I have been more or less struggeling to understand an equation that is apparently used in almost all books covering crystals in any way. Basically every book that I have found explains the following: ...
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2answers
45 views

Conductivity of a crystalline solid

In a crystalline solid each atomic level 'splits' into n levels (n = number of atoms in the system). When the number of atoms is large each level becomes replaced by a band of closely spaced levels. ...
2
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1answer
75 views

Experimental Evidence of Random Tiling Limit Shapes

In the area of random tilings, there are many results that fall under the term "Arctic Circle Theorems." This roughly means that if one chooses a tiling of a specific region uniformly at random, then ...
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0answers
19 views

How to derive the exponential distribution for the Pool-Frenkel effect?

For the Pool-Frenkel effect, the external electrical field $E_{ext}$ reduces barrier by a potential energy amount $U_{ext}(r_{m})$, where $r_{m}$ is the distance maximizing the total potential enrgy ...
3
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1answer
148 views

Difference between Wigner crystal state and fractional quantum Hall (FQH) state

Wigner crystal and FQH effect are both due to strong electron-electron interaction under magnetic field. As we know, Landau's symmetry-breaking cannot be used to describe FQH state. But can it be used ...
3
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1answer
1k views

Where are the ice rings in X-ray crystallography located?

I threw this image of one of my protein crystal's diffraction pattern (not the greatest) on a poster, and was wondering where (what reciprocal dimension) the ice rings are located as it might be a ...
9
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3answers
191 views

Are synthetically-produced diamonds as hard as natural diamonds?

I was having a discussion with my friend about the intrinsic worthlessness of diamonds (DeBeers and whatnot) and how synthetic diamonds haven't caught on, again because of the marketing/propoganda ...
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0answers
47 views

Diffusion coefficient of a crystal

I've been trying to work this out so I can give a hand waving argument for one of the effects I'm observing on the fly and I find myself going down a rabbit hole that seems way too complicated for ...
2
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0answers
103 views

Lattice theory in mathematics and physics

I have undertaken a project examining lattice model and trying to construct algorithm that could work on all lattice (in physical sense, or crystal structure). I notice there is a branch in ...
0
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1answer
212 views

Overview and doubts about Bloch's theorem and the concept of partial density of states

So I have a large confusion with QM as applied to solid state. The following is a summary of what I know, what I think I know, and what I know I don't know. I hope to stir a discussion that will help ...
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0answers
45 views

How does a liquid crystal on Silicon affect the phase of incident light?

When a polarized light beam is directed to a phase-only LCoS system how is the phase modulated ? What is the physical effect behind ? Does voltage modulation has an impact on birefringence ?