Crystal Definition and 382 Threads

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 ?

Homework Statement Write down the number of nearest neighbours in a FCC structure, calculate the angle between the bonds and the packing fraction. Homework Equations Literally don't know where to start! The Attempt at a Solution Very confused at the moment. Tried to look up...

Dear all, I'm coding the calculation of the free energy of an SiO2 crystal structure Using a 2-body Buckingham potential. I'm attempting to use the method of Frenkel and Ladd which consist in transform your solid reversibly into an Einstein crystal. I've read the excellent book...

Hi, I've got a random question. To my knowledge a liquid crystal filter bends incoming light coming in from various angles towards one particular angle as light leaves the filter. Does anybody know the % loss of light caused by this action?

Homework Statement A crystal growth furnace is used in research to determine how best to manufacture crystals used in electric components for the space shuttle. For proper growth of the crystal, the temperature must be controlled accurately by adjusting the input power. Suppose the...

Is there a way to represent resistance in a lasing crystal? If so, can someone tell me where to start looking? Thanks SF

Homework Statement Hey, the question is about delta function potentials V(x) = -g[... del(x + 3b/2) + del(x + b/2) + del(x - b/2) ...] going on out to a large x in either direction. a) sketch the ground-state wave fn, write the form of psi(x) for -b/2 to + b/2 b) show that e^z =...

Hello, can anyone help me out the the relationship of the atomic radius R with the lattice parameter a for a Hexagonal close packed cystals (HCP) and how to prove the ratio of a:C is 1.633. Any information on this issues would be appreciated. Thanks

Hi there, this is my first ever post in PF. Have you heard of crystal babies? They have been very popular among Taiwan students. And I have googled some information and some people said they consisted of "arcrylate polymers". They also said they are similar to Magic/Crystal Soil. Would...

Homework Statement Standing-wave vibrations are set up in a crystal goblet with four nodes and four antinodes equally spaced around the 15.0 cm circumference of its rim. If transverse waves move around the glass at 920 m/s, an opera singer would have to produce a high harmonic with what...

I have calculated the dependence of (1/s11) ie. single-crystal young's modulus on crystallographic direction for an inorganic crystal. I've noticed that certain peaks correspond to closely-packed planes eg. a psedo-hexagonal arrangement is seen in directions where the peaks (ie. local...

how would i start this solution off? we replace 7.5 atomic % of the chromium atoms in its BCC crystal with tantalum. X ray diffraction shows that the lattice parameter is 0.29158 nm find the density.

Homework Statement How many atoms are there in the unit cell of graphite? 2. The attempt at a solution I know graphite is hexagonal crystal structure. hcp also know that hcp has basis of hexagonal lattice which as 2 basis atoms. is there some other info i need because the answer...

I am working this problem... http://www.fiu.edu/~saulj/Teaching/Physics2/01-Electric_Force/CrystalStructure.html I got the answer to a as 0, but don't understand b.

So.. we've got a 2D crystal, corresponding an infinite square net with +-e0 charges in each one (see the atached photo). Now I'd like to calculate the constant k..when r goes to infinity... We = k (+-e0)*(+-e0)/(4 pi eps0 r)..on the positive charge in the center caused by the negative and...

or are they 1/8 of a sphere at the corners and 1/4 of a sphere at the edge?

Hi, I've got a question, I recently got interested in piezoelectricity. I almost no nothing about it tho. From the wiki artcile I gathered that when a force acts upon a piezoelectric material and deforms its shape, an electrical potential is created. I know that it has many applications in...

i want the formula of Angles Between crystal Planes by knowning the information of Miller Indices of that planes? please help me

Homework Statement Hello everyone, I'm a bit stuck on this particular problem and i was hoping somebody could give me a couple tips or hints! "consider a linear monoatomic chain where all atoms have a mass M except one which has a small mass m. The force constant is C." First I'm asked...

Standing-wave vibrations are set up in a crys- tal goblet with four nodes and four antinodes equally spaced around the 10:6 cm circumfer- ence of its rim. If transverse waves move around the glass at 900 m=s, an opera singer would have to produce a high harmonic with what frequency in...

I have a test after a few days and I face agreat deal with some concepts. Really I don't understand the crystal structure? how we know the Bravias lattice and how we get the primitive vectors and how we know the cells that make the lattice Bravias if it not? I want very clear...

I know acoustic and optical phonons can interact with one another. Also, longitudinal and transverse phonons can interact with one another. I am wondering can a longitudinal phonon in one plane act with a transverse phonon from another plane to create a third phonon? Or, do these...

Since the last thread got locked, how about legal means to get free electricity? One example is an AM crystal radio that receives it's power via a simple antenna. The power source is a radio stations broadcast. As posted previously, there are numerous devices like windmills or water...

Hi, I'm constructing an interferometry experiment, in which I'm using a Michelson-Morley-type interferometer. However, the only beam splitter I have which preserves polarization is physically small (a few mm), and so in my setup the beam in each arm is not split. The reflection off the mirror...

I think I understand the meaning and definition of the concepts of basis, cells, primitivecells and lattice, and so on. But could somebody please give me a short and consistent definition on crystal planes? For example on which level do you mean when you talk about these planes? Are they...

Is there any way to predict what crystal structure a pure metal element will be? It seems that the simple 'electron sea' idea does not explain a lot of things. Thanks -scott

Hi, Could I use the following item: http://docs-europe.electrocomponents.com/webdocs/03c4/0900766b803c41c7.pdf" to drive a piezo crystal to produce ultrasound? I know it wouldn't be perfect but it might be good enough for a small underwater depth sensor. Any ideas if it's possible?

I am looking for informations about CoIr alloys. Who can tell me about crystal structure, lattice parameters of CoIr alloy? Please share me some references about this material. Thanks! :!)

Does anyone here know of a good site explaining d_{xy}, d_{x^{2}-y^{2}}, etc. orbitals?

Hi, I am just wondering is there such thing as perfect crystal. I don't know much about this stuff. It seems to me it's just a theoretical idea, because nothing is really "perfect" in this world. Anyways, I just want to know more about perfect crystal. If they do exist, what is a perfect crystal?

Homework Statement Which of the following are true for the Crystal Field Model of an octahedral complex ion? Consider ions to be from first-row transition metals. a) Two of the 3d orbitals point directly at ligands b) t2 orbitals are less stable than e orbitals...

Homework Statement "Show that the C5 group is not a crystal point group." 2. Relevant information 1) "There exists another type of symmetry operation, called point symmetry, which leaves a point in the structure invariant" 2) "In crystallography, the angle of rotation cannot be arbitrary...

What is the approximate fractional difference in time measured between a quartz watch crystal resonating either normally or parallelly to Earth's surface gravitation?

i have a few questions: 1)what is the liquid used? 2)is the glass etched inside to hold the liquid or do they use a thin film of two layers, one conducting? 3)lcds use 180hz square waves to keep the display liquid black, but when just using dc the display will turn black and then fade, why?

hello! can anybody please tell me the difference between crystal and crystallite. thanks

Can anybody explain this thing that is "spin" to me? I basically came across it whilst researching how we know about the deep earth. Mineralogists and crystallographers talk about this thing called spin, quantum physicists also talk about spin; yet as far as I am aware they are they are not...

Do yall know of any good books on: crystal thermodynamics, crystalography, and phonons? I am looking for introductory books that assume knowledge of the basics like thermodynamics, calculus, etc... Any help would be appreciated. Thanks.

Homework Statement I'm calculating the distances between to nearest atoms from various planes an a cubic crystal. For example I know that the distance from the [111] plane to the nearest atom is for a fcc lattice d=\frac{\sqrt{3}a}{3} What I'm unsure about is where the 1/3 factor...

friends i studied abt the crystalline structures of compounds but i am just failing to understand the defects of the crystal lattice so i hope some one will help me in sorting out this problem of mineo:)

The distance between the primary planes of a NaCl crystal is 2.82 Å. It was found that the first order Bragg reflection of a monochromatic x-ray beam occurs at sinus= 10 degree. (i) Determine the wavelength of the x-ray. (ii) Determine the angle, sinus for a second order reflection.

I know this might be a really stupid question, but to convert a crystal lattice 2D representation to a 2D reciprocal lattice do you justdo you just invert the scaling. I know this is a pretty poor explanation so I will try and illustrate what I mean. Let's say that you have a reciprocal lattice...

hey guys...im stuck with this experiment of an Electrical Analogue Simulating a crystal Lattice...could anyone explain me the whole concept of relating a set of LC filters to a crystal lattice?

Hello, I am new to this forum and guess what :P my first post is going to be a question, well, a few. Why do crystals form at low temperatures? What physics are involved with this? are there any articles on this subject (ive tried looking, but havnt found anything so far)? thanks!

Hi, I have the following problem : I generate GaAs (zinc blende structure) supercells, and then I want to replace some As atoms by N atoms. Let's say I have fcc conventional cell repeated twice in the x, y and z direction so that I have a total of 64 atoms, 32 of Ga and 32 of As. 8 atoms...

what's the difference between those two?