The study of how the properties of matter arise from its structure at all scales and of how processing can be used to modify those properties (often in pursuit of a specific application).
6
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2answers
138 views
+50
Ferromagnetism with mobile spins
How can electron spins in Iron at room temperature have ferromagnetic order even though they are travelling at very high speeds?
One could argue that spin and motion are completely uncorrelated and ...
1
vote
1answer
34 views
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 ...
2
votes
0answers
33 views
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 ...
0
votes
1answer
46 views
What is tricritical point？
Critical point is the transition temperature of a second order phase transition. But what does tricritical point mean? WIki says that a tricritical point is a point in the phase diagram of a system at ...
1
vote
1answer
39 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 ...
2
votes
3answers
95 views
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.
2
votes
2answers
51 views
What materials focus EM radiation in the 2.4GHz range
If glass and similar materials refract visible light effectively, what materials would be best for focusing lower frequencies of EM radiation, if any? If not, what other methods exist for focusing ...
0
votes
0answers
33 views
Material physical properties of a desk related to vibration propagation?
I'm a software programmer (not a physics expert) trying out a smartphone vibration detection algorithm on desks, and I want to measure the impact of the desk's material features on the algorithm. Are ...
0
votes
1answer
39 views
What limits the maximum sustainable surface charge density of a sphere in space?
Suppose I charge a sphere and leave it in vacuum for 10 years. After that time, I want its surface charge density to be in the order of 10^5C/m^2. Would that be possible? Would it depend on the ...
0
votes
0answers
15 views
Is resilience a measure of power expended upon unloading?
I read the definition of 'elasticity' and 'resilience on Wikipedia:
Elasticity is a property of materials which return to their original
shape after they are deformed.
Resilience is the ...
4
votes
2answers
135 views
Graphene +1 extra carbon bond
I'm not a physicist just a curious mind, so please go easy!
I was just watching a BBC Horizon Documentary that featured a piece on the recently discovered material Graphene. One of the facts ...
0
votes
3answers
69 views
Accelerating faster per second than the speed of sound?
What would happen if you were to accelerate one end of a material, say a steel rod for instance, at faster per second than the speed of sound in that material?
For example, if the speed of sound in ...
0
votes
3answers
73 views
Hooke's law limitation question
Let's consider a spring. I am a strong man(well, lets assume) and I am pulling the spring. the work I do is being stored in the spring in the form of its elastic potential energy. Then suddenly, ...
3
votes
4answers
143 views
Effects of surface roughness on specularity
Say you have a piece of glass, which looks specular if propery cut/polished. But if you sand the surface using say sand paper, it will look hazy and glossy. I'm wondering how much surface roughness ...
1
vote
2answers
59 views
Equation describing magnetic hysteresis
So when you're looking at B-H curves for ferromagnetic substances, you often see these magnetic hysteresis curves, which occur, I gather, largely because of domain formation which has some reversible ...
3
votes
3answers
255 views
Why is copper diamagnetic?
Cu has an unpaired electron in 4s, but it is diamagnetic. I thought that it has to be paramagnetic. What am I missing?
4
votes
1answer
57 views
Thermal conductivity affected by electrical current
Does anyone know of any materials whereby the thermal conductivity can be changed by passing an electrical current through the material?
0
votes
1answer
145 views
Acoustic Metamaterials: Negative Bulk Modulus?
In acoustic metamaterials we have simultaneously negative bulk modulus, $\beta$, and effective mass density, $\rho$.
I understand how one can obtain a -ve $\rho$ by constructing a solid-solid system ...
1
vote
3answers
38 views
Trapping EM radiation
Is there a material which can allow light (or any other EM radiation) to pass through from one side as if it is transparent but its other side reflects light like a mirror?
0
votes
1answer
67 views
Can we make a space elevator/lift?
Is it possible to connect a long rope (excluding the danger of it's breaking) to a geostationary space station and use it to transport food and other necessary item's to the station and then ...
2
votes
3answers
163 views
Why does a spring lose its energy when compressed for a long time?
Why does a spring lose a part of its energy when compressed for a long period of time? Is it because the material gets bent?
0
votes
0answers
77 views
Whats the contact area for elastic contact between a cylinder and a plane surface?
I am trying to determine the contact area between a cylinder and a plane surface of two different materials so that the plane lies tangent to the cylinder. There is elastic contact between the two ...
2
votes
3answers
119 views
Glass pipe cutting
I want to know how to quickly create the straightest possible breaks in glass pipes
I apologise if this is only borderline suitable for a physics forum - I just hope experts with a lot of experience ...
1
vote
1answer
130 views
Calculation of number density from material density
Material density is given by $ \rho =m/V$, where $m$ is mass and $V$ is volume.
Again number density given by $n=N/V$, where $N$ is the total number of particle. How can I calculate number density $n$ ...
5
votes
2answers
123 views
In mechanics, is shock really better expressed as jerk instead of acceleration?
Some expensive electronics or mechanical devices are designed to be shock-resistant. However, the manufacturers often market the level of shock-resistance in units of g-force (I know g-force is really ...
1
vote
1answer
171 views
Learning roadmap for solid state physics [duplicate]
I am a PhD student in mathematics who knows little more about physics than what one learns in high school. For my research on tilings of space and aperiodic order, every now and then I have to skim a ...
0
votes
1answer
41 views
Optical refocusing efficiency
What is the material for optical focusing that produces the less diffraction losses?
Suppose one have a sequence of serial optical elements $R$ that keep refocusing a beam of collimated light, each a ...
0
votes
1answer
430 views
Calculation of a bending moment
I'd like to calculate the bending moment of a cantilever, fixed at its base, and submitted to a certain stress on a specific spot, but I can't find the proper definition of this bending moment (first ...
1
vote
2answers
380 views
Vibration as a means of passing through solid objects?
First of all, I think this is a weird question but I still want to know whether it's possible. There is a character in a cartoon network series who is really really fast. Sometimes he lets his own ...
0
votes
0answers
31 views
Does graphene actually remain strong for macroworld engineering?
I heard that people envision strong structural materials made out of graphene, but I heard it may weaken when being stack in layers. Is graphene viable for macroworld structural engineering or is it ...
0
votes
0answers
28 views
Piezoelectricity [closed]
I want to do a science fair project in piezoelectricity, any ideas on what I can do?
I want to do the crystals first then perhaps connect them to a lamp. However, I think it's normal. Can anyone help ...
0
votes
2answers
336 views
Materials with a high compressive strength to weight ratio
We know about extremely strong materials such as carbon nanotubes. However, this is only in tension. What are some high strength-to-weight materials (both available and hypothetical) in uniaxial ...
2
votes
0answers
54 views
How can I determine the type of magnet used in a DC motor?
I repair electrical motors in a workshop and sometimes I must repair permanent magnet DC motors and other motors that use permanent magnets. I need to specify type of permanent magnet (Ferrite or ...
2
votes
1answer
194 views
Intuitive description of what a “Fermi Gas” really is?
This question is based in the area of material equations of state. I am wanting to know what a Fermi Gas really is. I have searched in several places for a decent description, but I have not found ...
0
votes
1answer
56 views
Is there real materials have Lieb lattice structure? [closed]
Is there real materials have Lieb lattice structure?
Some examples?
-2
votes
1answer
78 views
Lightest flying solid material [closed]
I need to use a number of lanterns, to write something with it!
I would like to use a light material which will bind the lanterns together (separated by space) so it looks like dotted letter.
I know ...
8
votes
2answers
181 views
Shape of wall's deformation wave caused by baseball's impact
Clicking through this year's top sports pictures, I stumbled upon this one. I was wondering about the shape the baseball is leaving on the wall.
What phenomenon causes this peculiar shape? Why is ...
2
votes
1answer
112 views
(Botanical) branch bending under gravity
I'm a PhD student in maths, and attended my last physics class some 15 years ago, so you can imagine my competences in the field.
My supervisor (also not a mechanist) cant tell me how to proceed ...
3
votes
1answer
201 views
Why does glass break at the line where you score it?
Why does it take such a small incision for the glass to break at that spot? Why is the structural strength of the material influenced by such a small imperfection?
1
vote
1answer
82 views
Semiconductor problem: how much Boron is required to establish a certain amount of charge carrier density
The problem description is as follows:
Boron is used to dope 1 kg of germanium (Ge). How much boron (B) is required to establish a charge carrier density of 3.091 x 10^17 / cm^3. One mole of ...
3
votes
1answer
271 views
Transparency of solids using bandgaps and relation to conduction and valence bands
I think I understand how a solid can appear transparent as long as the energy of the photons travelling through it are not absorbed in the material's bandgap. But how does this band gap relate to ...
3
votes
1answer
106 views
What states of matter are possible at lowest temperature?
Near absolute zero, some materials are superconductors. Other materials are superfluids. Others are Bose-Einstein Condensates.
Is there a complete list of possibilities? Or is this still a research ...
4
votes
4answers
3k views
Does glass get stronger the longer its under water?
I was reading the internets and I saw an image of of random facts. Yes, I know, its a humor site, but based on the image item #23 I have some questions.
Does glass really get stronger the longer its ...
0
votes
1answer
85 views
Characteristics of bloch electron in a priodic potential
Effective mass of a Bloch electron in a periodic potential is negative why ?
4
votes
0answers
41 views
Order of magnetic phase transitions
Is there any phase transition occur in paramagnetism to diamagnetism transitions state. What should be the order and how will I calculate the order?
0
votes
0answers
111 views
Phase diagram problem for ternary system
For a ternary system, three composites are present.
Temperature is also a variable.
Assuming that pressure is held constant, what is the minimum number of phases that may be present in a ternary ...
2
votes
1answer
71 views
Is shear elasticity the same as shear modulus?
I've encountered both the terms "shear elasticity" and "shear modulus". Are these the same?
1
vote
1answer
84 views
Why can we analyse force balance on a dislocation?
Dislocation (like screw or edge dislocation) is not a 'real' thing, while Newton's laws only apply to a real object (no matter macroscopic, like stars, or microscopic, like atoms).
In the derivation ...
1
vote
4answers
140 views
The requirements for superconductivity
Which properties are sufficient evidence for a material to be not superconducting?
I am looking for a set of statements like
If the material is semiconducting, it is not superconducting
Edit:
I ...
1
vote
0answers
50 views
Is it possible to increase refractive index at lower densities?
Are there any materials for which the refractive index decreases with density? It seems that for most materials we would expect there to be a positive correlation between density and refractive index, ...
