Crystal Definition and 382 Threads

Dear all, I am recently dealing with crystals. There is one question which puzzles me a lot. How to calculate the energy of crystals? For example, tungsten oxide has severl polymorphs such as alpha, beta , and gamma. What is the energy difference among them. Hope you can help with this...

Suppose that a static electric field E is applied on a conductive crystal. Then, how quantum mechanics describes the electron movements in the crystal? I have been trying to find an explanation, but have not found any. As I understand it, we could treat the E field as a time-dependent...

Homework Statement Use a computer to calculate numerically the potential energy, per ion, for an ifinite 2D square, ionic crystal with separation a; that is, a plane of equally spaced charges of magnitude e and alternating sign. Homework EquationsThe Attempt at a Solution The closest I can...

In explaining x-ray diffraction of crystals, usually the approach is to consider the atoms absorb radiation and scatter it, at some angles constructive interference occur and bright spots can be observed. It seems that it is different from the diffraction of slits or gratings because in these...

How much does a Piezoelectric crystal (say PZT) compress when applied the maximum amount of force it can withstand ? also it would be very helpful if someone could tell me how much is this force typically ?

it makes sense that with an inelastic scattering process, a wave approaches a crystal, and then some energy is imparted to the phonons, so that the outgoing wave has a different frequency from the incoming wave. However, with an elastic scattering process, the frequency is unchanged-- how does...

Hi, I have a question. If a crystal absorbs light and the absorption process leads to some excess energy being released as heat . Can one calculate the temperature rise or an experiment would most certainly need to be done? Apart from the heat capacity of the crystal before light absorption...

I am wondering how can I solve following problem. I would like to see how can it be solved.

Homework Statement The polyacetylene chain is a 1D chain of Carbon atoms with single bonds and double bonds in succession. Spacing for single bond is ##a_s = 0.144~nm## and spacing for double bond is ##a_d = 0.136~nm##. Describe the structure using a "lattice" and a "basis". Sketch the...

Why are atoms taken to be spheres, and not of some other shape, in the calculation of the packing fraction of different crystal lattices? In other words, what experimental evidence and theoretical reasoning motivates this form of the atomic shape?

Hello, I've been having some trouble with a paramagnetism problem from my Statistical Mechanics class textbook (F. Mandl, Statistical Physics, 2nd edition, p. 25). The problem is as follows 1. Homework Statement 2. Homework Equations 1. The temperature parameter \displaystyle{ \beta =...

I had a roommate that is a regular user of meth. I recently found out that smoking meth leaves a residue behind that can be absorbed through the skin, which worries me because I let him borrow my car and he smoked meth in it before. I'm kind of a hypochondriac when it comes to health issues like...

Hi, I am currently reading the Feynman Lectures on Physics, and I have just finished the chapter about the geometry and the symmetries of crystals, and there is something I do not quite understand. There are 230 different possible symmetries which are grouped into seven classes (triclinic -->...

Homework Statement A simple model for liquid crystals confined to 2 dimensions is o assume each molecule can only align in one of 2 perpendicular directions. To construct a landau model its convenient to define order parameter, s : s = 2 ( Np - 0.5Nt ) / Nt Np - number molecules...

Hello! I know how to calculate band structure and density of states of photonic crystal (example is pic.1) Does anybody know how to plot such DOS maps? The second picture is from the article about photonic crystal fibers by Rodrigo Amezcua.

Hi everyone, I'm trying to simulated the XRD pattern of Bi2Sr2Ca2Cu3O10, but I'm having a problem of finding the basis of atom(and their respective position). Also its JCPDS is quite hard to find, so if anyone working with this, may you provide a link or articles about my problem. Thanks...

We know the rule of cross product or Why here |absinΘ| = , and = c cos Φ in the above picture? Thanks for explanation.

GaAs crystal structures have basis atoms: Ga: (0 0 0), (0.5 0.5 0),(0.5 0 0.5),(0 0.5 0.5) As: (0.25 0.25 0.25),(0.75 0.75 0.25),(0.75 0.25 0.75),(0.25 0.75 0.75) i'm trying to find intensities at all of its plane, using this equation: I = (F^2)*m*Lf (m= multiplicity, Lf=lorentz factor)...

Hi All, From the Schrodinger wave equation, I kind of understand what a wave function and hence a wave vector is, so I understand what a wave vector of an electron wave is. However while talking about crystals, there is also a 'crystal wave vector'. Is this a vector sum of wave vectors of...

Given only 2theta and intensity, how to know the crystal structure (except cubic) of non cubic crystals, and also determine their lattice parametera,b,and c, if there's a link or website discussing techniques to determine crystal structure of all crystals, please don't hesitate to put it here...

Hi guys, I'm assume that you already know the 7 crystal system, each crystals have unique way of determining the family of planes, for example in cubic, we all know (111) plane is same (-1-1-1), and so on ((-1-11),(-11-1)...) a total of 8, in fact there is pattern to determine how many possible...

My high school chemistry teacher tossed us the task and told us to figure it out ourselves. As far as I can understand, the trick is to supersaturate the solution, put a seed on a string and hope for the best. I'm just posting here to ask if anyone happens to know any good sites I might not have...

Hi All! A little background info. I'm working with cardiac pacemaking devices with the overall scope of implementing piezoelectric energy harvesters into the devices. I'm in the initial stages of research and development. Okay, so this is my conundrum: I have an output pulse circuit as shown...

For violet phophorus,it seems that the crystal structures given by two websites are not the same.In Openstax CNX,the link is http://cnx.org/contents/f46e8679-ee00-4073-9f5e-a87ca9955a9e@25.9:67/Chemistry_of_the_Main_Group_El and the Figure 12 displays it as follows: But in Chemwiki,the link is...

Homework Statement I'm trying to hook up crystal oscillator package on breadboard and test for expected operation: I'm not sure how and cannot find any data sheets for the pin connection diagrams, I attached an image I found of the kind of package I'm using. There are four pins. Homework...

Hi Guys, please help me. how can i derive the primitive vector of copper oxide (I)? basically this is cuprous oxide having a cubic crystal structure but since it has oxygen in it the directions and magnitude of primitive vector are far different compare to basic cubic structure. also please help...

I'm working on a school project that requires me to build a RF oscillator that is able to be started and stopped at about 100kHz. Ceramic or crystal oscillators would be good because of their tiny size, however, the high Q factor creates a problem. So my question was, can placing a resistor in...

Hey all, This is a problem I can't really wrap my head around. 1.) The lanthanoid series is formed through the progressive filling of the 4f subshell, whereas the first row transition metal series is formed through the progressive filling of the 3d subshell. a) What is the relative...

Background information: The wave function for an electron in a crystal lattice is modeled by a Bloch wave. A Bloch wave is a function with the periodicity of the lattice multiplied times a complex exponential function. This exponential function has a wave vector k, called the crystal momentum...

Hey guys, I'm actually had a hard time in figuring out about our assignment in crystallography of semiconductors, the problem said that, Identify the atomic line lattice axes in a, b,c axis and basal plane diagonal, face plane diagonal, and body plane diagonal of TiO2 and Aluminum Nitride...

in my previous thread i was trying to build a sine oscillator and an amplifier. decided to give up on the idea and purchase. any chips out there that can give me 30-40volts peak to peak. the frequency is not an issue as long as it is above 1 MHz. i guess i can use any crystal oscillator as long...

So i don't really understand why the change in momentum of a crystal involves a reciprocal lattice vector. Surely it is just the change in momentum due to the change in the number and frequency of the phonons before and after whatever event/scattering/collision takes place. Can somebody please...

Suppose I have a substance that has been crystallized. Now suppose I break down those crystals into powder, grains, etc. How can I reconstruct that powder into a crystal again? Do I just dissolve it into a solvent and then evaporate the solvent? Another quick question - is it possible to...

I was inspired by this article http://science.howstuffworks.com/environmental/green-science/house-music-energy-crisis1.htm to wonder if one could put piezoelectric crystals in the sole of a shoe and perhaps harness the energy to charge their iPod?Can someone let me know if this is feasible and...

Say we have a one dimensional chain of N mass points separated by springs of spring constant k. This system can be quantized? Let the quantized system above be at rest and let one of the end mass points emit a photon of energy E along the crystal axis. Will we get physics similar to he...

Can someone please tell me the basics to how a cystal radio works? And also what are all the components that makes up a crystal radio? Thank you!

What are the high symmetry directions for a two-dimensional oblique crystal? Please provide a figure of the corresponding Brillouin zone with high symmetry points labelled.

Hi, I'm hoping I'm in the right section, I wasn't quite sure. For a couple of days I've been trying with no success to make a crystal radio. To save me the trouble of having to build my own components, I decided to build a tuned circuit that should resonate at a radio frequency (and insert...

Hi guys, I am a new user of QCM and I am having trouble reaching equilibrium. I have isolated the chamber from air flows and vibrations, the crystals are clean and all the other removable parts have been cleaned as well. The real problem is that sometimes I have managed to reach equilibrium...

Hello, I bought an electronics kit for my 12 year old brother (and perhaps a little for myself too...) for building a crystal radio. I would like to understand what's going on when I tune the radio, so that I can explain it to him. It's a simple setup, where changing the position of a...

Hello, Could someone please explain crystal momentum in understandable terms? Thanks, EV

Homework Statement A crystal lattice consists of a spin 1 particle at each lattice point. Spin 1 particles can have z-components of magnetic moment that take on the values +μZ, 0, and -μZ. In an external magnetic field B, each spin can have an energy U = -μZB, so the possible energies are...

Hi, I'm looking for a simple s.s crystal unit cell structure and can't find it anywhere. I understand that stainless steel is a very general word and takes many forms and has many different types, but isn't there a standard type that people use in the industry and ususlay talk about when they...

So my dad got this Salt Crystal Lamp for a wedding gift that supposedly freshens the air naturally, and I need some help explaining to him why this doesn't actually work. It says on the box: "This lamp is scientifically proven to work like an air purifier. When lit, it can emit negative ions...

Does atoms in a crystal have energy states like electronic states? it is according to Einstein relation for harmonic oscillator.E=nhw

Hi, I have problems with the following: Number of modes for a 2d crystal with one atom per primittive unit cell. 1. Number of discrete vibrational modes? Should there be 2N of them? That is what I come up with if I think of one transverse and one longitudinal mode for each k. But I am...

Hi all. we know that the rest is the mass of an object within a coordinate system which has zero velocity, but how does it exist for an electron inside a crystal, which we call rest mass of electron, how electron exist with zero velocity.or we mean by zero velocity of electron with respect to...

Is it possible to predict, at least in theory, which shape a crystal of some combination of atoms would have. If so, what are the principles for such a calculation. I have seen a theorem in classical thermodynamics called wulfs theorem about the equilibrium shape of crystals. Does this explain...

I want to calculate the surface energy for the (001) plane in a simple cubic lattice. My idea is this: When I cleave a simple cubic crystal I create 2 surfaces each sharing an amount of broken bonds. I want to find the amount of broken bonds per area, because I can associate an energy with...

Homework Statement Identify the [221] vector? A B C D E Homework Equations The Attempt at a Solution I reduce [221] to [1 1 0.5].BUT after getting the wrong answer, the feed back is as follows "Feedback: [221]: has a 0.5 component along the x-axis...