Crystal Definition and 430 Threads

What is the volume of atom/volume of cell?

Homework Statement In a mock exam I was asked for Q. Two properties associated with a single crystal. Homework Equations The Attempt at a Solution For one answer I gave that they are hard. I think another answer might have been something to do with crystal...

Dear friends, I am doing a Molecular dynamics simulations of a crystal. For this the initial configuration is FCC (face centered cubic) lattice. My problem is that I have to study the system for different orientations of the crystal i.e. (100) plane, (110) plane and (111) planes. For (100), the...

There is a crystal structure relationship for circular birefringence which can tell you if a crystal structure will have circular birefringence and its handedness (left,right) (e.g. "On the origin of optical activity in crystal structures" J. Appl. Cryst. 1986. 19, 108-122, A. M. Glazer and K...

There is a crystal structure relationship for circular birefringence which can tell you if a crystal structure will have circular birefringence and its handedness (left,right) (e.g. "On the origin of optical activity in crystal structures" J. Appl. Cryst. 1986. 19, 108-122, A. M. Glazer and K...

Homework Statement Localize the image of an object situated at 1.2 m from a crystal ball with a diameter of 0.2 m (n=1.5). Homework Equations None given. But Snell's law I believe. The Attempt at a Solution I'm totally stuck at starting. Does the size of the object matters...

The problem said: "Determine the magnitude of the Schmid factor for an FCC single crystal oriented with its [100] direction parallel to the loading axis. " The Schmid factor is the "cos(\phi)*cos(\lambda)" term in the equation for resolved shear stress. I know that the slip planes...

I'm not a native English speaker so I need some clarification about the term "nonlinear gain" concerning a laser experiment. In detail I'm working on a lab report where I'm supposed to estimate the nonlinear gain of a KTP crystal in a Nd:YAG LASER using the intracavity second harmonic...

Hello all, I am attemtping to model crystal twinning using DFT methods. In particular I wish to look at the twin energy as a function of twin angle in a hcp system. I am running into difficulty however in attempting to create my repeat unit prior to my calculations. I was wondering if...

Hello, is there any detailed table about the s,p,d,f,etc level splitting due to various crystal symmetry(like O,Oh,D4h,...). I think it should be somewhere since it is a well established material. Can anyone help?

Hello everyone, I am trying to understand COMSOL 3.5 and I am interested in Photonic crystal fibres and tapered optical fibres. First of all, could you please tell me what is the background of the layout? When you create a design/object, the rest area is air or I need to define another object as...

Metals with what type of crystal lattice less prone to brittle fracture? Why?

When I was a little kid, I met a gemologist who showed me a cool trick with a ring he'd bought for his wife. When he submerged it in water, the crystal disappeared! As I now know, this crystal had an index of refraction of 1.33. Anyone know what this crystal is and/or how I can get my...

1. Homework Statement Using the powder XRD data below, show that the substance has a face centred cubic structure. (xray lamda = 0.154056 nm) Peak No.------2(theta) 1 -------------38.06 2 -------------44.24 3 -------------64.34 4 -------------68.77 5 -------------73.07 2...

Homework Statement Using the powder XRD data below, show that the substance has a face centred cubic structure. (xray lamda = 0.154056 nm) Peak No.------2(theta) 1 -------------38.06 2 -------------44.24 3 -------------64.34 4 -------------68.77 5 -------------73.07 Homework...

Hello I need your help! Using XRD, I detected single crystals (single peak) on the surface of a bulk specimen. My guess is that the structure is most probably Zr2Cu, but a distorted one. I know that Zr2Cu structure is MoSi2 type, spacing group of I4/mmm, tetragonal. I want to ask 1)...

Energy Gaps in a Spacetime Crystal L.P. Horwitz, E.Z. Engelberg (Submitted on 14 Oct 2009) This paper presents an analysis of the band structure of a spacetime potential lattice created by a standing electromagnetic wave. We show that there are energy band gaps. We estimate the effect, and...

My teacher this year assigned us to do an alum crystal growing lab by ourselves, so we find the procedure and do a related theory all by ourselves. In my group i was doing half of the related theory and i basically had questions i had to answer. The question i am stuck on is, "5. Once the...

Hi, I have this quite basic question regarding photonic crystals. As I understand, a periodic dielectric structure (photonic crystal) has modes (spatial profiles) at discrete frequencies from: \nabla \times \Big( \frac{1}{\epsilon(r)}\nabla \times H(r) \Big) = \frac{\omega^2}{c^2} H(r)...

Can entangled protons be maintained in a crystal lattice for an indefinite period of time? The following papers seem to support this contention. I need the help of the Forum’s readers to critique this research and the assertions the authors are making. Dr. Francois Fillauxa and Dr Alain...

I want to know the basic principle of working for quartz crystal microbalance, how it is used to measure the thickness of the film?And why it can work at room temp (with water cooling) and at higher temp say 65deg ??

Homework Statement Calculate the potential energy, by ion, in an infinite bi-dimensional ionic crystal. Hint : Use the power series expansion of \ln (x+1). Homework Equations \ln (x+1)=\sum _{i=1}^{\infty} \frac{(-1)^{i+1}x^i}{i}. The Attempt at a Solution W=U=k\sum...

Homework Statement The unit cell in a cubic crystal is 2.74Å. Determine the Bragg angle for reflections from the planes (200), (212) and (-112). [sorry i don't know how to put a bar on top of the numbers] if the x-ray wavelength used is 1.54Å Homework Equations Given Bragg's condition as 2d...

Hi, I am having trouble with the following: All I have really done is differentiate the function to give an expression for F(r), but I am a bit clueless about the rest. How can there be equilibrium if the two ions are attracted to each other? Cheers, GeoffreyThelm

Hey. I want to derive the conductivity of graphene. I'm looking for a formula of the sort: J = \frac{e}{\hbar} n \frac{dE}{dk} D(E) \Delta E where \frac{1}{\hbar} \frac{dE}{dk} is the electron velocity, D(E) = \frac{dN}{dE} is the density of states, \Delta E might be the applied voltage...

Setup: I'm trying to make the band structure for a planar photonic crystal with finite thickness, i.e., a quasi-3D problem. I only want the x-direction band structure. So, I'm using variable floquet periodic BCs for the x-direction boundaries, and 0 degree floquet periodic BCs for the...

I have some questions about CSL (coincidence site lattice) boundaries between crystal grains. 1. What is the relation between twin boundaries and CSL boundaries? Is it true that all twin boundaries are CSL boundaries, but not vice versa? Is the energy of twin boundaries even lower that the...

What can this crystal be? Hello, I have some crystals with the following properties which I am unfortunately unable to find out their chemical formula or name... any other material with the following characteristics will help too. Cubic with octahedral habit. RI : 1.5 - 1.6 Density...

number of electrons leaving crystal surface. any help :)? [b]1. A scanning tunnelling electron microscope (STM) measures a tiny electrical current tunnelling out of the surface of a crystal. The current is 0.30 pA (0.30 x 10-12 A). Calculate the number of electrons per second leaving the...

Homework Statement You wish to study a crystal's structure by diffracting thermal, non relativistic neutrons from the crystal, so you go to a nuclear reactor and set up your diffraction experiment on one of the neutron beam lines. The neutrons emerge from the reactor with a range of...

What difference would you observe about the yield stress, young modulus,etc if your material were a single crystal? Explain the difference.

I heard that it is possible to measure positions of individual atoms in a crystal. Is this true? I understand the principle of measuring crystal orientation and base vectors of Bravais lattice with X-ray, but I have no idea how positions of individual atoms can be obtained. I suppose it is...

Hi all, I have a doubt regarding interaction energy term between atoms of crystal. 1.) Actually in interaction energy term of Inert gas crystals, we get term as R**(-12) as repulsvie potential. But on the contra while writing term for Interaction energy term for Ionic Crystal we write Repulsive...

Hello, I was wondering if we can deoxidize Iron inside a crystal like Kyanite (Natural form), which contains Fe inclusions (sometimes rusty)... Thanks in advance.

I am new to this website but I would like to know how to build a homemade radio using an electro magnet and a germanium diode crystal. Are ther any other components required to complete the construction of the radio?

Hello, I have this ongoing argument with my professor. I read in a paper (friction and wear) that the crystal structure can affect friction. HCP crystal structures having lower friction coefficients. I have two papers that mention this in passing one, linking FCC crystal structures to have...

Are there stress and strain graphs for different crystal structures?

Homework Statement The distance between the Li+ and Cl- ions in a LiCl is .257 nm. Use this and the molecular mass of LiCl 42.4 g/mol to compute teh density of LiCl.Homework Equations The Attempt at a Solution I am surprisingly having a lot of difficultly with this problem. The LiCl crystal is...

Homework Statement X rays with wavelength 0.10 nm are incident on a crystal with a hexagonal crystal structure. The x-ray diffraction spectrum is shown in the figure. Figure: What is the atomic spacing D of this crystal? (in nanometers) Homework Equations The Bragg...

Homework Statement Choose an instrument to measure the output from the crystal, when measuring variations in stress. The maximum voltage from the crystal is 200mV. current in circuit is 2 x 10-8 A, p.d is 4 x 10-15 full scale deflection, sensitivty...

This was just the coolest thing I have ever seen. I'd love to go there and see it in person. http://news.nationalgeographic.com/news/2007/04/070409-crystal-cave.html

Homework Statement A mono-energetic beam are of neutrons is directed perpendiculary at the surface of a metal crystal whose atom are a constant distance 0.1E-10m apart. The scattered beam of neutrons is found to have maximum intensity at an angle of 25degree to the initial direction. What is...

Homework Statement Because the book gives me little information about the cross slip. So I can't handle the basic problem below. I appreciate that you can give me some hints or suggestion. An f.c.c crystal is deforming by motion of disslocations on the (a/2)[101](11-1) (I use minus instead of...

Homework Statement The atomic mass number of copper is A = 64. Assume that atoms in solid copper form a cubic crystal lattice. To envision this, imagine that you place atoms at the centers of tiny sugar cubes, then stack the little sugar cubes to form a big cube. If you dissolve the sugar, the...

When setting up this derivation one assumes a chain of identical atoms. The interatomic interaction between atoms is short ranged and so only affects neighbouring atoms (see Hook and Hall, "Solid State Physics" chapter 2.3.1). The potential V(r) is expanded as a taylor series about r = a to...

Hey All.. I'm having some problems trying to understand the tetrahedral and octahedral sites in face centered cubic (fcc) and body centered cubic (bcc). It is hard to visualise the structures in 3D.. I wanted to know how to find out the positions per unit cell for the tetrahedral and...

Hi all I am new here but i have a major question, iv been told by people that this question is easy but I am just going around in circles with it and i was wondering if you could help. here is the questionAluminium cystallises in the fcc structure with a single atom basis. the lattice constant...

I've just read an article about IT with light instead of electrons: http://focus.aps.org/story/v22/st15 I wonder, is there any indication that light processing will be faster than conventional electronics? Information transport is faster, but what about logic operations? What would be...

If a salt crystal forms after 3 days of evaporation, and the crystal mass is 30 mg, how many Na+ and Cl- ions was added to the crystal each second (average). How do I solve this?

at crystal field stabilization in strong field case d4 CFSE=-16Dq+p d5 CFSE=-20Dq+2p d6 CFSE=-24Dq+2p d7 CFSE=-18Dq+p d8 CFSE=-12Dq it was shuld be +3P and +4 P why it be +p,2p,2p,p ?