All Questions
Tagged with crystals material-science
85 questions
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Binding energy in metallic crystals
I have a question regarding metallic bonds.
Let's say that I have an iron crystal (Body-centered cubic bavais lattice), the bonds between iron atoms are (obviously) metallic bonds but i dont know how ...
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3
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27
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What causes these 2nd order knot shapes and why?
I twisted a (broken) rubber band around multiple revolutions. Initially it created what I call first order twists, where the "wave-length" of the twist got shorter and shorter across the ...
- 61
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35
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Electron microscopy and Interatomic distances of miller planes
I am studying Transmission Electron Microscopy (TEM), and have been seeing in articles TEM images of different materials typically come accompanied by these diffraction patterns, caused by the ...
- 548
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47
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Structure factor correct calculation
I have a set of 2D points and wish to test it for hyperuniformity.
As I've learned from papers, the good idea is to calculate structure factor $S(\mathbf {q})$ and test it for
$$\lim _{\mathbf {q} \to ...
- 163
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67
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What is the unit cell and the bravais lattice of a perovskite?
First year PhD. student here. I keep trying to wrap my head around what kind of bravais lattice and how does the unit cell of a perovskite look? I am specifically interested in bismuth ferrite (BiFeO3)...
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Are there any materials known to be harder than diamond under high pressure as of April 2024?
This is a variation of this question where I asked if materials under high pressure can break standard pressure density records.
I am curious about materials that become superhard under very high ...
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1
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123
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Why are there triclinic and monoclinic lattices, but biclinic is never mentioned?
When classifying the Bravais lattices we have the
triclinic (point group ${\rm C_i}$) and the monoclinic $({\rm C_{2h}})$ cases, but we do not see the "biclinic" case listed. Why not?
It ...
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28
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What happens when slip direction is the same as applied force?
Using the equation
$$ \tau R = \sigma y \cos \left( \phi \right) \cos \left( λ \right) \tag{1} $$
means that when the angle $\phi$ between the tensile axis and slip plane normal is $90$, $\cos \left( ...
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2
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110
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Why don't all metals have closed pack structures?
A lot of times, in my materials classes, metal atoms' behavior during deformation is described like a bunch of stacked balls. In my introduction to material class, our professors explained that metals ...
- 3
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33
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Structural notation for multi-element FCC crystal structures
I was wondering if different compound FCC structures share any kind of indicator or structural notation which I could use to find and categorise them.
To clarify my problem: the FCC L12 structure, ...
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1
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56
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How to calculate Lennard-Jones potential for a crystalline material?
Suppose that we have the unit cell of a crystalline material. We want to calculate the Lennard-Jones (LJ) interaction energy between an hydrogen atom at a point $\mathbf{r}$ (inside the unit cell) ...
- 1,688
3
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129
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Are solid materials ergodic systems?
It is stated that a system is considered ergodic if it can access all available states with the same energy in the phase space over long periods of time and that time average and ensemble average of ...
- 31
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28
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Why delocalized states cannot exist in 2D systems
In "Topological Insulators and Topological Superconductors" by Bernevig and Taylor, it is written on page 60:
In a seminal paper, Laughlin argued that the presence of
edge modes is an ...
- 592
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1
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117
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What are the visible differences of single-crystal and polycrystals?
I saw a question where it supposes a particle of quartz sand with 1 mm in diameter is opaque white. I am then asked on whether this particle is single-crystal, or polycrystal. Admittedly, I am quite ...
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3
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Why does the the dielectric constant of a ferroelectric increases with temperature, below $T_C$?
The above figure is taken from C. Kittel.
When a ferroelectric substance (say, BaTi${\rm O}_3$) at room temperature is gradually heated, the dielectric constant $\varepsilon_r$ first increases and ...
- 12.3k
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93
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Can oxides of uranium be used to color aluminium oxide based gemstones, or diamonds?
Rubies and sapphires are chemically equivalent to the mineral corundum, with the exception of transition metal impurities that impart different colors to the aluminium oxide. Uranium is not a ...
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Are reciprocal lattice basis vectors parallel to their corresponding real lattice basis vectors?
So I had a question asking to find the angle between b* and (113) plane normal in a tetragonal unit cell. I know that the angle between two plane normals are given by:
My thinking was that if I know ...
- 11
3
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1
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227
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Can sound waves affect the regularity of crystal positions in stone as it cools?
I've long wondered if it would be possible to hear the speech of ancient peoples by scanning sequential imperfections in crystal formations of fire-side stones as they cooled down and solidified (for ...
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3
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3k
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What causes this frost pattern on my windshield?
I was walking back to my car yesterday when I noticed the frost on the back windshield formed these long "straight" lines:
The temperature was about -10C and I was wondering what the ...
- 91
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1
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401
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Quasi-periodic potential and Bloch's theorem
Let's look at a physical system of a particle in a one dimensional periodic potential $V(x)$. When the potential satisfies the periodicity condition of the form
$$ V(x + n b) = V(x),$$
this leads to ...
- 257
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1
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67
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What do the '4' and 'b' signify in a layer of a crystal called a '4Hb' crystal or material?
From Phys.org:
Study gathers evidence of topological superconductivity in the transition metal 4Hb-TaS2
Which, in turn, references:
Abhay Kumar Nayak et al, Evidence of topological boundary modes with ...
- 4,699
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1
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94
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Why do inorganic lasers not experience problems due to triplet loss?
A major problem for building organic lasers (especially if aiming for electrical pumping) is the creation of triplets that cannot classically photoluminesce (forbidden transition) and can interact ...
- 19
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1
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694
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Why is diamond harder even though its packing fraction is only about 34%?
Why is diamond harder even though its packing fraction is only about 34% (less than that of fcc)?
- 165
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1
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35
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How does a materials modulus of elasticity (proportional zone ratio) relate to crystal defects?
I'm studying biomedical engineering and I'm about to take "Biomaterials" (basically materials science applied to medicine) final exam. In one recorded class, the professor mentions the ...
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1
answer
1k
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Why is lead soft?
As most of us know, lead, at room temperature, is quite soft. You can easily bend a lead rod. You can easily scrape a small piece off it with your nail, and you can even pull a thin long piece apart. ...
2
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108
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How is ECR (Electron Counting Rule) done in a structure?
I've been told how to apply the ECR to GaAs{001}(2×4) in my lectures but it makes no sense to me and I don't seem to be able to find any other sources that explain this. (This is a further question on ...
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1
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170
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Which is the correct GaAs{001}(2×4) structure?
When trying to understand the GaAs 2x4 surface reconstruction, I came across the following statement:
"Because the periodicity of the surface has doubled (compared to the bulk periodicity) in the ...
- 759
2
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1
answer
53
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How come we can grow nanowires? Semiconductors
I'm not a physicist by background but I'm interested in semiconductors and am trying to understand third generation semiconductor material technology. In some of the roadmaps for the 2nm and 3nm chips ...
- 21
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1
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206
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Does sugar have a quasi-liquid film on its surface at room temperature?
Background
According to an article from Physics Today, ice is slippery because there is a “liquid or liquid-like layer” on its surface.
There are 3 mechanisms that can cause this layer to exist, each ...
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213
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2
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1
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382
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What are the best resources for Crystallography?
I am undertaking a module in nanosurfaces and I was unaware that I would require some knowledge in Crystallography. The information that I must know regarding this area are Miller indices, Symmetries, ...
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16
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Quantify/visualize atomic clusters in multi-component crystalline materials
Let's say we have a material $AB$. Is it possible to detect atomic clusters of A atoms experimentally?
The size of clusters in question: 2 atoms (nearest neighbour (nn) pairs), 3 atoms (nn triangles), ...
2
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0
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153
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What happens at the boundary of the Brillouin Zone?
I believe that at the boundary of Brilluoin Zone i.e, at -π/a,π/a. Taking k=π/a we have k=2π/λ
so λ=2a. Making the group velocity zero. Does it point to Braggs law? What does it really signify?
- 21
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58
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What is an incommensurable grain boundary?
As the title states, I'm unsure what it means to be a commensurable or incommensurable grain boundary (when discussing dislocations and small angle grain boundaries). I see the term being used ...
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3
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3k
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Why no proton microscopes? Proton diffraction; or proton scattering experiments? Proton crystallography?
I am asking a (relatively) 'low-energy' question here, not about things like the Large Hadron Collider...
There are tons of articles everywhere, including such places as Wikipedia and ScienceDirect, ...
- 4,699
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1
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101
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Relation between $(hkl)$ indices and the integers $m_i$ in $\vec{G}=\sum_i m_i\vec{b}_i$?
Can somebody explain how to establish the connection between Miller indices $(h,k,l)$ of a crystal plane and the triplet of integers $(m_1,m_2,m_3)$ that appear in the linear combination $$\vec{G}=...
- 12.3k
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1
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98
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Clarifications about definition of Bravais lattice
I have a doubt about the definition of Bravais lattice for periodic materials.
Precisely, here it is defined as:
a discrete set of vectors closed under vector addition and subtraction
If I look at ...
- 1,329
3
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1
answer
2k
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What is an "As-grown crystal"?
I was going through a paper on a material. In that paper the authors mention "as-grown crystal".
I tried looking for it on Wikipedia and searched it online but none of them tell what it is. So can ...
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4
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1k
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Why do metals have a crystal structure if their electrons are delocalized?
It is said that metals have an electron structure that is delocalized; their electrons are not strictly bonded to the atoms but rather form an irregular "sea" of electrons.
I'm studying materials ...
- 911
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1
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5k
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Equation for the multiplicity of a set of planes
The multiplicity (m) of lattice planes counts the number of planes related to (hkl) by symmetry. For example, the multiplicity of the {100} planes would be 6 because the following planes are all ...
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1
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1k
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Steinhardt order parameter and radial distribution function
Is there a relation between the probability distribution of Steinhardt order parameter for BCC and FCC and their radial distribution function?
In the picture we see the probability distributions of ...
- 115
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1
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230
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A one-dimensional periodic structure is the simplest type of photonics crystal and any such one-dimensional system has a band-gap?
My textbook says the following:
A one-dimensional periodic structure, such as a multilayer film (a Bragg mirror), is the simplest type of photonics crystal, and Lord Rayleigh showed that any such ...
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173
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What is a ferroelectric metal?
I was reading online about ferroelectricity, and came upon the topic of ferroelectricity in metals. The main cited paper is the one below by Anderson and Blount in the 1960's
Symmetry Considerations ...
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731
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How are the orientations and cuts of crystal substrates determined?
I have been looking at piezoelectric crystals, LiNbO3 primarily, so piezoelectric devices. But I have had trouble understanding the cuts and orientations that are referred to with the rotated cuts.
...
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1
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650
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Negative Miller indices and parallel planes
The integers are usually written in lowest terms, i.e. their greatest common divisor should be 1.
https://en.m.wikipedia.org/wiki/Miller_index
Does this mean, that parallel planes are generally ...
- 135
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1
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885
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Points of symmetry in $k$-space
Can you relate a point in the reciprocal space with a vector in real space?
How do I find the family of planes that represent a point of symmetry in the Brillouin zone?
For example, germanium has ...
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0
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33
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How to estimate the mobility of atoms implanted in the interstitials and/or vacancies of a crystal?
I would like to compare the likelihood for implanted helium atoms to move from interstitials/vacancies of a crystal versus neon atoms. I read in the literature that He atoms located in interstitials/...
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57
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Using Miller indices to determine interference from a particular plane in a crystal lattice
In terms of x-ray diffraction from crystals. I was wondering how you can use the miller indices to determine whether there will be constructive or destructive interference from a particular plane in ...
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1
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982
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How to visually understand that dislocation moves on a slip plane?
When we look at images of edge or screw dislocation, it seems as if the direction in which that dislocation will move is already fixed by the 'way the dislocation is present'. For example, take any ...
- 87
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1
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82
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A metallic container when hammered deforms but a wine glass when falls or hammered breaks. Why?
A wine glass breaks when it falls from hand or is hammered. But when a metallic object (say, a container) is hammered, it only deforms without breaking. Why? Is it somehow related to the fact that ...
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