In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid.

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Why does phosphorous give a free electron in silicon doping?

Extrinsic semiconductors are created by doping an intrinsic semiconductor; typically silicon is doped with phosphorous to create free electrons or boron to create "holes". In the case of phosphorous ...
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25 views

Why is Cubic closed packing called “cubic”?

How is Cubic Closed Packing "cubic" and also how is hexagonal closed packing "hexagonal" ? I have been thinking over this since a few hours but I am unable to visualise. I understand that when ...
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193 views

Why are there only 7 types of unit cells and 14 types of Bravais lattices?

Why are there only 7 types of unit cells and 14 types of Bravais lattices? I was reading about solid state chemistry for the first time and this limitation made no sense to me. I tried to do the ...
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30 views

How do we identify left handed and right handed crystals?

I was going through this article about how Louis Pasteur studied and explained the absence of optical activity in Racemic acid. Here's an extract: When Pasteur next examined crystals of the ...
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Fermi Level of an alloy

How could one calculate the Fermi level of a copper-nickel alloy? They are both structurally face-centered cubic, however how would this structure affect the Fermi level of the individual atom or the ...
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15 views

How would I find an apporpriate dopant element for a lattice

I am trying to figure how would I go about finding a dopant element that would fit in a copper lattice? I already have the data for the atomic dimensions and structure (available below), however how ...
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65 views

Why do we not see silicon in a structure like graphite?

Silicon exists in a structure similar to diamond, with 4 silicon atoms bonded to each other in a tetrahedron. Why do we not see it exist in a structure like graphite? Is it even possible to get ...
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22 views

Why does the dielectric constant of a solid increase due to a Frenkel defect?

In crystalline solids, an atom may be displaced from its original position in order to create a vacancy in the original location. This is referred to as a Frenkel defect. Why does this defect result ...
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33 views

Calculating Molar Volume from crystal volume

I am trying to calculate molar volume of certain crystal lattices to be used for crystal growth kinetics calculations. The information I have is the crystal volume & crystal lattices. For example ...
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98 views

Why is SiO2 solid while CO2 is a gas?

I was under the impression that chemistry almost exclusively involves valence electrons because there isn't enough energy to strip off electrons located closer to the nucleus. If that is true, and ...
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29 views

What bond\crystal has the most regular pattern (i.e. least irregularities)?

Salt is a famous regularly repeating cubic crystal, but there are always natural deformities and flaws present. I have heard that graphene is an extremely uniform substance. With these in mind, what ...
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59 views

Pyramid Structure Name

I would like to know what the name is for the structure drawn below. This looks like a pyramid with 4 atoms at each vertex. Does the name of the structure depend on whether the atoms are all the same ...
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131 views

data repository of organic compounds

Does there exist any data repository of chemical compound that gives the structure of the compounds with the help of coordinate geometry. It would be like each atom has a coordinate and the list of ...
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31 views

Solidification of sodium polyacrylate

Sodium polyacrylate is a white powder with a characteristic odor. But when we add water to this powder, instead of forming a aqueous solution , it instantaneously solidifies and forms more amount of ...
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130 views

Number of atoms in NaCl

Consider this picture of an $\cf{NaCl}$ unit cell: It appears to show 14 $\cf{Cl-}$ ions and only 13 $\cf{Na+}$ ions. Given that discrepancy, how is table salt balanced for charge? Why isn't ...
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30 views

Extracting “Crystal Radii” from a CIF file

I'm currently downloading .cif files from various online databases and using openbabel to convert the fractional coordinates that are in the .cif files into .xyz files. The typical output will look ...
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48 views

What are the structures of potassium superoxide and xenon hexafluoride? [closed]

I have 2 questions in mind: 1) What is the structure of the superoxides? More specifically, what is the structure of $\ce{KO_2}$? 2) What is the structure of and dipole moment for $\ce{XeF_6}$?
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60 views

Finding large databases of sphere packings

Part of my research is investigating sphere packings and their properties.I really would like a large database of sphere packings that I could investigate using a program I have written that tells me ...
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46 views

Are there any early industrial age methods capable of determining diamond or graphite's crystalline structure?

I'm writing a fictional story with early industrial age technology where a chemist discovers not only that diamond and graphite are made of the same substance, but that they differ by crystalline ...
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Elements of symmetry [duplicate]

Which are the elements of the Twofold Screw Axis 2/3 in this image (green line)? The blue Dots (1/3- and +)?
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R32 Space Group

Which are the elements of the Twofold Screw Axis in this image? The "+" and "-" elements that intercept the red line are the elements of the Twofold Screw Axis 2/3? And if so, is the height of the ...
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41 views

Real space term for PPPM vs PME

I was under the impression that differences between the various long range electrostatic algorithms, ewald, PME, PPPM, to name a few, lied solely in their treatment of the reciprocal space term. ...
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32 views

Shapes of ionic compound

Can anyone explain the shapes of ionic compounds? What does it mean? What does the coordinate number mean? I know that in $\ce{NaCl}$, one $\ce{Na}$ atom is surrounded by 6 $\ce{Cl}$ atoms, and vice ...
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46 views

What determines the elastic limit of a substance?

from what I know, the elastic limit of a substance is the maximum amount of stress/force/pressure (a bit of confusion on my behalf here) a substance can withstand and still return to its original ...
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What factors contribute most to solubility of ionic substances in highly polar solvents, esp. ionic liquids and DES?

I am trying to determine a method to dissolve a mineral salt with a lattice energy of ≈18000 kJ/mol. I know that lattice energy is the most significant factor affecting solubility of an ionic ...
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Why are so many ionic compounds brittle?

Even when ionic compounds are strong (e.g. rubies and sapphires), they are neither malleable nor ductile in the slightest, and if sufficient stress is put on them, they will shatter, not bend. Why is ...
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212 views

What is the difference between an amorphous solid and glass?

They are both formed when a liquid is supercooled rapidly, no free energy, and they both have irregular structures. What defines a glass other than how it is amorphous, transparent, and has a glass ...
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101 views

R32 Space Group (Crystallography)

Why R32 Space Group is so named? I mean, if R stands for Rhombohedral and 3 for Threefold Axis, what 2 stands for? I don't see any Twofold Axis in the cell: ...
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Do Crystals have stronger intermolecular bonds than amorphous solids?

Do Crystals have stronger intermolecular bonds than amorphous solids and are the properties of amorphous solids vs. crystals explained by their structures?
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50 views

Finding Ice CIF files in crystal database

Could anyone please tell me where I could find the the structure of cubic ice (ice Ic) as a .cif file? I have been searching the cambridge structural database using "H2O", "water", "dihyrogen oxide" ...
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38 views

How to compute the NMR shift in Gaussian09 for only one specific atom in a bigger unit cell?

I am trying to compute the NMR shift for a specific atom in the middle of the surrounding crystal unit cell (1 surrounding anion sphere and 1 cation sphere) in Gaussian09. I only need the chemical ...
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55 views

How are piezoelectric crystals made?

I want to know how the powdered formed of piezoelectric material is converted to crystal like used in quartz watches. I know that some more chemicals are mixed with the material and then it is pressed ...
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149 views

How to add hydrogens to a crystal structure

PDB protein crystal structures most of the time lack hydrogen atoms. Usualy I use PyMOL (h_add) but it does not always seem to be giving the correct result. What ...
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36 views

What is omega and nu in this expression?

In the picture below a proportionality equation is shown: $$\omega \propto \nu \exp\left(\frac{-\Delta G_m}{RT}\right)\propto \dots$$ While $\Delta G_m$ is the Gibbs free energy, $R$ is the gas ...
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Why do some crystal structure files not include bonds?

Why do some crystal structure files not include bonds (the atoms are just placed in the respective position in the cell without bonds between any atoms)? Shouldn't the bonds always be there? Also, ...
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Deformation of the nematic phase of liquid crystals surviving in the solid state

Does anyone know if I were to cool a liquid crystal with a deformed nematic phase quickly, if it will preserve the deformation in the crystal lattice? I didn't find any information in classical ...
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76 views

How would one construct a 3D model of a molecule based on the crystal structure of its salts?

Often crystal structures found online from past published crystallography experiments are of the salt of a molecule of biologic interest, as opposed to the freebase form of the molecule itself. For ...
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What things form crystals? [closed]

Just getting interested in this stuff. People are saying I should crystallize salt, for example. What things could I do instead of salt with and still get a crystal from? Thanks a ton!!
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Crystal field theory for calculating lattice parameters

If I have an 8-coordinated metal cation (e.g., $\ce{Te}$, $\ce{Nb}$, $\ce{Ta}$, $\ce{Sb}$, $\ce{Bi}$, $\ce{Zr}$, $\ce{Hf}$) by oxygen anions, is there a way to theoretically calculate the structure of ...
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41 views

Can bone mineral be obtained in pure, crystalline form?

Can bone mineral be obtained in pure, crystalline form outside a living organism? Had this been done ever?
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Structure of Ca2B6O11

What is its structure? I found an image of $\ce{B6O11}$ unit but it looks incorrect: The top left corner one. The oxygen can make max 2 bonds but $\ce{O8}$ has three! There are six ...
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How to determine the Bravais lattice and atom basis vectors from a CIF file?

Say I have a CIF file describing some material in terms of its symmetry space group, lattice parameters and in-cell atom positions. A simple example might be, ...
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Modified DNA bases in Pymol and Coot

When using Pymol or Coot molecular visualization software to solve x-ray crystallography structures, how can I mutate a cytosine to a 5-methylcytosine?
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76 views

Theoretical Calculation of Lattice Parameter from Space Group

If I am given a compound which belongs to, say the cubic $\text{Ia}\bar 3\text{d}$ space group, is there a known way to calculate the lattice parameter of the compound? In general, can lattice ...
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24 views

How to predict if hydrogen atoms could be placed in the interstials of a lattice

Palladium hydride is an example of a hydride which contains H atoms in palladium's crystal lattice (which is fcc). I would like to know if it's possible to predict if another hydride, $\ce{NbH_{x}}$ ...
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Determining structure factors for crystals from lattice and motif

I understand that the structure factor for a crystal is given by: $$F_{hkl} = \sum_r f_{r} e^{2{\pi}i(hx_{r}+ky_{r}+lz_{r})} $$ My textbook (''Structures of crystals'', Glazier) suggests that you ...
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Why is sand/glass polar? How does lattice structure change polarity?

The molecular geometry of sand is linear. Dipole moment is thus cancelled. But we all know from the meniscus water makes with glass that the dipole-dipole/H-O attraction between sand and water is ...
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Can chemicals change crystal structure by only touching?

Are there any known, or suspected compounds that take the crystal structure of what ever object they are touching, i.e. if it touches $\ce{NaCl}$ it would turn into a face centered cubic crystal ...
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Is there any required data missing from my CIF file?

I previously asked a question about a CIF file here (namely CIF fields that are available for some atoms, but not others) I think I have the answer (namely to place dots [.] at places where the two ...
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CIF fields that are available for some atoms, but not others

I've been working on another CIF file, this time for (-)-threo-methylphenidate based on Pharma Res, 1995 (sadly the relevant crystallography data isn't supplied in the free preview at Springer). I ...