The crystals tag has no wiki summary.
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What does the wavevector $\textbf{k}$ mean?
In Ashcroft, Mermin Solid State Physics, Eq. 17.43 is
$$
\epsilon(\textbf{k}) = \frac{\hbar^2 k^2}{2m} - e\phi(\textbf{r})
$$
where $\textbf{k}$ is the wavevector and all other symbols have their ...
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1answer
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localized electrons in the crystals
Why electrons in low lying levels of individual atoms stay localized in their own atoms in a crystal? Doesn't this contradict Bloch's theorem?
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If my lattice has an atomic basis, do I also find the reciprocals of the basis vectors to get the reciprocal crystal structure?
That is what my crystal structure looks like. The blue atoms sit on every lattice point (basis vector of $\{0,0\}$) and the red atoms have basis vector of $\left\{{2\over3},{1\over3}\right\}$. The ...
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1answer
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Is this 2D structure triclinic?
The only rotation axis obvious to me is rotation by 360 degrees, the identity. Vertical mirror planes I've been dicing and cutting it through several planes and I still see none. Yet, the structure ...
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1answer
42 views
What would be the basis vectors for this 2D crystal structure?
In the above image, I have a 2D crystal structure. The lattice vectors are described by:
a = {-1/2, -Sqrt[3]/2};
b = {1, 0};
and the location of atoms A and B ...
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3answers
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What is the difference between lattice vectors and basis vectors?
Google has not been very useful in this regard. It seems no one has clearly defined terms and Kittel has too little on this.
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1answer
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Why do lumps of sugar break more easily when blowing in it?
My question is simple, when you have a small lump of sugar, it's hard to break it with your bare hands, but when you blow in it, it appears to be more easy. (it's a piece of advice i learned for my ...
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1answer
45 views
I can't figure out crystal planes with negative intercepts
As seen above, I don't follow how you figure out those planes. It seems they're not using the origin labeled. I'm not really sure I understand spatially what's going on in the left figure so let's ...
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What are some applications of crystal fabrication? [closed]
I have heard of some applications here or there in certain papers, but I am looking for a broader scope of examples.
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39 views
To which real densities do carrier densities in the semi-classical model of a crystal correspond?
In the semi-classical model of a crystal in solid state physics, electrons and holes are assigned effective masses that account for their different mobilities. E.g. in silicon, holes have a bigger ...
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1answer
74 views
Algorithm for identifying planes in a Bravais Lattice
I have a lattice with Lattice Vectors $(\vec{t}_1,\vec{t}_2,\vec{t}_3)$ which are NOT orthogonal in general.
How can I identify the atoms/unit cells that belong to a plane - that is normal to a given ...
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0answers
29 views
pressure required for displacing a single electron off a crystal
I need to know this for my project- "power generation using the pressure applied on a keypad of a mobile electronic device". How much pressure does it take to displace a single electron off its ...
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1answer
60 views
Estimate the difference between two sets of atoms
I've been working on amorphous structures derived from a crystalline one (using MD) containing $N$ atoms. I want to prove that these structures are different and to quantify their "differentness". One ...
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1answer
87 views
Direct and Reciprocal lattice common point
Does a reciprocal lattice have a common point with its direct lattice?
(possibly at the origin $\vec{K}=\vec{R}=\vec{0}$)
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6answers
228 views
Entropy and Crystal Growth
I was reading about growing single crystals and I'm a little confused about this -
In most crystal growing processes, a "seed crystal" is used, and the rest of the material crystallizes on the seed ...
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0answers
65 views
How to find the translation vectors of a primitive cell when primitive cell encloses multiple atoms? [closed]
How to find the translation vectors of a primitive cell when primitive cell encloses multiple atoms?
Your help is appreciated!
Thank you!
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2answers
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Crystal visualization software for visualizing lattice with reciprocal vectors drawn in same image [closed]
I'm looking for a free crystal visualization program, preferably for Linux, that can visualize the common lattice structures in 3D interactively (rotatable with mouse) and draw in the same picture the ...
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0answers
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How does a snowflake “know” to form symmetrically? [duplicate]
Possible Duplicate:
Why are snowflakes symmetrical?
Under ideal situations, a snowflake forms into near perfect hexagonal symmetry. How? For instance, when a water molecule moves towards ...
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2answers
74 views
Is it possible to have annealing without creep?
Annealing can repair a material by allowing atoms to find the minimum energy state; since solids have a surface tension this process will allow cracks to fuse and reverse fatigue. However, annealing ...
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1answer
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Dichroism in uniaxial crystals
I need a same help with it. Some books where i can find a real math explanation of this effect will be good help!!
simple exp of this effect will be good too)
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0answers
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Crystal momentum and the vector potential
I noticed that the Aharonov–Bohm effect describes a phase factor given by $e^{\frac{i}{\hbar}\int_{\partial\gamma}q A_\mu dx^\mu}$. I also recognize that electrons in a periodic potential gain a phase ...
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1answer
56 views
Is there real materials have Lieb lattice structure? [closed]
Is there real materials have Lieb lattice structure?
Some examples?
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0answers
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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 ...
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Why do phonons cause excellent heat conduction in diamonds?
Phonons are the quantum of lattice vibrations in crystals and are not to be confused with photons, the gauge bosons of the electromagnetic force. Apparently, they contribute to heat conduction, but I ...
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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
293 views
Derivation of Bloch's theorem
I'm having a problem following a derivation of Bloch's theorem, looking at a one dimensional lattice with $N$ nodes and spacing a, we impose periodic boundary conditions, meaning that the ...
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Bandgap Spacing in Photonic Crystals
I am doing some self-study on photonics and have encountered the following question:
We know that amorphous electronic crystals such as amorphous silicon have a bandgap. Can amorphous photonic ...
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What material has the highest packing factor? P3HT or PCBM?
I need some help with something I've been unable to figure out. Both P3HT and PCBM do have a semicrystalline nature.
However, which of these material has the biggest change in density (that is, the ...
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Bragg condition for transmission: Why is the full diffracted angle Two times Theta? Or isn't it?
On a Bragg reflection with incomming angle Theta the total diffraction angle of the incomming wave is 2*Theta, of course.
But I have Bragg transmission with electrons on a graphite crystal ...
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1answer
101 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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Does positronium have a stable crystalline phase?
This is a long shot, but while the 100YSS conference is going on at Houston, i haven't been able to get a grip on myself and think in other, more mundane and short-term rewards as normal people do. ...
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Discrete sum over an exponential with imaginary argument, considering only every second lattice site?
Let's say I sum an exponential function $e^{\imath \left(k-k^{\prime}\right) x_{i}}$ over a chain system where every member of the chain is of the same type, e.g.,
A-A-A-...-A-A (total of N sites)
...
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1answer
91 views
How to estimate number of Laue Spot
Why are "Laue Spots" spots instead of rings? Or is there an effective way to estimate the number of Laue spots? I can't find any formulas or theory concerning this issue. Thanks for your attention!
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How does the process of freezing water remove salt?
How does freezing water to make ice remove whatever salts were in the water to begin with?
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Wyckoff positions and lattice coordinations
Many papers use Wyckoff positions and Space Groups to report atom coordinates, making use of the structure's symmetries to save space in the notation (e.g. diamond = Fd-3m, only).
How can I ...
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1answer
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Born-Oppenheimer Approximation equivalent to Tensor-product ?
If you have a wave function $\Psi$ of a system consisting of an electron and the vibrational modes of the crystal, THEN we represent the wavefunction $\Psi%$ to be in the Hilbert Space formed by the ...
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3answers
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What are local electrons in a crystal?
I am reading Pekar's "Research in Electron Theory of Crystals" and I came across a passage I find a bit unclear:
The theory developed below takes into account the dielectric
polarization of a an ...
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1answer
496 views
How to write the Fröhlich Hamiltonian in one dimension?
I am currently working on a (functional) analysis problem refining Pekar's Ansatz (or adiabatic approximation, as it is called in his beautiful 1961 manuscript "Research in Electron Theory of ...
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1answer
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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 ...
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Does a thermally expanding torus experience internal stress?
I'm trying to learn continuum mechanics and thermo-mechanics.
As we know, heating an object increases the mean atomic distance $a_0$ of the atoms in a rigid body. Let's assume it is a linear elastic ...
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4 digit Miller Index for a cubic structure?
As the title states, can a Miller index for a cubic structure have 4 digits? If I have a structure with intercepts (2,8,3) on the x-y-z axes respectively, the following Miller index would be (12,3,8), ...
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The 2011 Nobel Prize in Chemistry
As far as I understand a new pattern of crystal growth has been found experimentally. How does it relate to the known 2D and 3D nucleation and growth of crystals? The dominating theory of crystal ...
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Why is the crystallography restriction obeyed?
The crystallography restriction states that any 2-dimensional lattice can have rotational symmetry of degree 1, 2, 3, 4 or 6 - and that's it. A simple proof of I've heard of this is: the magnitude of ...
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How to make a single crystal silicon wafer?
How can I make a single crystal silicon wafer? What are the tools needed? What is the most diffcult part? Can I make it at home or at school lab?
I am now interested on Czochralski process where you ...
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What defines the thickness of a Nomarski prism?
Lets say I want to design a Nomarski prism that would split the ordinary and extraordinary beam by an angle of 0.32 mrad. I used a raytracer to find the internal angle between the quartz wedges.
...
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Transparency of materials
Is transparency of material has something to do with inter- or intra-molecular bonding? E.g. both graphite and diamond are carbon, but graphite is opaque and diamond transparent.
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Madelung constant list (for surfaces as well)
Searching for this on google proved to be quite tedious, but I reckon that someone working with crystals a lot might know this off the top of his head:
Is there a good source that lists the Madelung ...
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1answer
367 views
Nature of tetragonal distortion in Jahn-Teller effect
I am wondering: If I have a regular octahedron as my starting point, oriented along the x-y-z axis, and now Jahn-Teller suggest I elongate or compress along the $z$-axis, what happens along the other ...
