Physics Stack Exchange
Physics Stack Exchange

Questions tagged [crystals]

Crystals are solid material whose constituents, such as atoms, molecules or ions, are arranged in a highly ordered microscopic pattern, a crystal lattice that extends with regularity in all directions. Use for all crystallography and ordered structure topics.

Crystals are solid material whose constituents, such as atoms, molecules or ions, are arranged in a highly ordered microscopic pattern, a crystal lattice that extends with regularity in all directions. Macroscopic single crystals are usually identifiable by their characteristic geometrical shape, consisting of flat faces with specific orientations.

1075 questions
217
votes
1 answer

Strange ice found in my garden

This morning I found a really strange ice formation in my garden. I can't figure out how it appeared, because there was nothing above. The night was particularly cold (Belgium). To give an idea, it has the size of a common mouse (5 cm of Height and…
snoob dogg
  • 1,717
65
votes
3 answers

Is it possible to "see" atoms?

As per my knowledge, atoms are small beyond our imaginations. But there is an image on Wikipedia that shows silicon atoms observed at the surface of silicon carbide crystals. The image: How can we see these distinct atoms if they are so small?
jNerd
  • 923
44
votes
3 answers

What is the smell after quartz is rubbed together?

When I rub quartz together, it glows due to triboluminescence but it also creates a burnt smell. What causes that smell?
The Seal
  • 413
34
votes
1 answer

Why are snowflakes flat?

There have been many questions and excellent answers in this community about the symmetry of snowflakes, e.g., here and here. There is however one aspect of snowflakes that does not seem clearly addressed: Why are snowflakes flat? One reason could…
Roger V.
  • 68,984
33
votes
1 answer

Understanding time crystals

In very recent publications, two groups in Maryland (paper: "Observation of a Discrete Time Crystal") and Harvard (paper: "Observation of discrete time-crystalline order in a disordered dipolar many-body system") have separately worked on…
user929304
  • 4,910
31
votes
5 answers

Is crystal momentum really momentum?

Almost every solid state physics textbook says crystal momentum is not really physical momentum. For example, phonons always carry crystal momentum but they do not cause a translation of the sample at all. However, I learned that in…
skywaddler
  • 1,515
27
votes
3 answers

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, that talk at length about probing condensed matter…
Kurt Hikes
  • 4,767
  • 3
  • 19
  • 41
25
votes
4 answers

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 factor given by…
Alex Eftimiades
  • 643
  • 4
  • 11
24
votes
8 answers

Why don't marbles naturally arrange themselves like a crystal?

Most solids are crystalline in nature because the energy released during the formation of ordered structure is more than that released during the formation of disordered structure such that the crystalline state is the lower energy state. So if we…
user342326
  • 369
22
votes
4 answers

Why does ice have a lower density than water?

Can someone explain me why is ice less dense than water? As I know, all solids are usually denser than the liquids (correct me if I am wrong).
Gil
  • 883
20
votes
4 answers

"Lack of inversion symmetry" in crystal?

Apparently (first paragraph of this article) the lack of inversion symmetry is some crystals allows all sort of nonlinear optic phenomena. Now. Does anyone know of an intuitive or just physical explanation as to why this is the case? What does…
SuperCiocia
  • 25,602
19
votes
2 answers

Why do crystals grow in preferred directions?

I want to know why snowflakes (and other crystals) grow symmetrically and I find the leading answer to the established question to be entirely unsatisfactory. When water freezes, you get ice. Ice, like many solid materials, forms a crystalline…
spraff
  • 5,256
18
votes
1 answer

Interpretation Born-Von Karman boundary conditions

The cyclic Born-Von Karman boundary condition says that if we consider a one dimensional lattice with length $L$, and if $\psi(x,t)$ is the wavefunction of an electron in this lattice, then we can say that $\psi(x+L,t) = \psi(x,t)$ for every $x$.…
Rayman
  • 1,031
18
votes
6 answers

Why are phonons quantized?

I'm a third year physics major taking an introductory subject on condensed matter physics. I'm trying to understand the concept of phonons in a 1D lattice. I understand the classical treatment of (1D) lattice vibrations (wikipedia has a derivation…
LittleJollyBoat
  • 370
16
votes
2 answers

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 that natural diamonds are "better". My friend,…
Bigbio2002
  • 263
1
2 3
…
71 72