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

learn more… | top users | synonyms (2)

0
votes
1answer
37 views

How do I write a valid CIF, PDB or XYZ file from the coordinates listed below?

I want to create a 3D molecular file using coordinates taken from: Hrynchuk, RJ; Barton, RJ; Robertson, BE (1983). "The crystal structure of free base cocaine, C17H21NO4" (PDF). Canadian Journal of ...
3
votes
1answer
55 views

Empirical formula of Berthollides

Can the empirical formula be defined for berthollides? Is it equal to the molecular formula, or it can't be defined?
3
votes
1answer
38 views

Miller indices. What determines the appropriate axis?

So, first of all, what's up with this "plane" I see two planes! The basis of my question is that to determine miller indices the plane cannot lie on your origin, so you have to make a translation. ...
1
vote
0answers
23 views

Central Atom in EXAFS

I read somewhere that EXAFS (Extended X-ray absorption fine structure) gives us the distances between central atom and its neighboring atoms. Is that true? Why can't we get the distance between two ...
1
vote
0answers
16 views

Two-dimensional Networks of Coordination Polyhedra

Does anyone know of any references that use {V/P, P/V} notation? This involves polyhedra joining to form polygons, or vice versa (this is where my confusion lies) V/P may refer to the number of ...
1
vote
1answer
50 views

Determining perovskite crystal structure

I've been reading that perovskite presents a sort of pseudocubic crystalline system, however it can be stretched and suffer modifications to become orthorhombic etc. The thing is, if I consider it ...
2
votes
1answer
30 views

What's the most efficient way to find crystal structures of drugs?

I'd like to be able to find the crystal structures of drugs, for example at the moment I want to find the crystal structure of (R)-fluoxetine so that I can use Jmol to create an accurate 3D model of ...
4
votes
1answer
72 views

Determining the Packing Geometry of Compounds

I'm a little confused on the method to determine packing geometry. The question I'm given is Determine the packing geometry of the following compounds by using the radius ratio rules. For your ...
20
votes
3answers
2k views

Carbon atoms at the edge of a diamond

It is well known (the simplest textbook example) that a diamond has a well-defined arrangement of sp3 carbon atoms, as each atom is connected to four others in a ...
1
vote
1answer
27 views

Approach to model solvent in a lattice: e.g. H2O in NaCl

If a lattice contains a solvent, lets say NaCl and water of crystallisation, what is the condition for a solvent molecule to change it's location? From my current point of view I assume that such a ...
1
vote
1answer
48 views

Grocery store crystalline citric acid

Which type of citric acid crystalline powder do they sell in grocery stores? Is the concentration of citric acid in the crystals 100%?Is it anhydrous or a monohydrate?
2
votes
2answers
41 views

Represent bonds spanning a unit cell boundary plane

Is there a chemical input format that is- Supported by Open Babel (and hence supports visualization in avogadro??) Can represent a bond connecting an atom to its partner in a neighbouring unit cell, ...
0
votes
1answer
42 views

What happens when ice melts?

What happens when ice melts? I have this question, with two possible answers: regularly arranged molecules change into irregularly arranged molecules water molecules become less densely packed ...
2
votes
1answer
35 views

how to determine timescale with characterization methods?

There are as classified in the Atkins textbook 4 different timescales on material characterization: a)Time during which a quantum of radiation or a particle can interact with a molecule. b)Lifetime of ...
0
votes
1answer
47 views

Dihedral angle of gaseous and crystalline HOOH

Why does hydrogen peroxide exhibit a dihedral angle of 111.5 degrees in the gaseous state? And a dihedral angle of 90.2 degrees in the crystalline phase? I know that in general, there is likely to ...
5
votes
1answer
42 views

Is there a systematic way to determine the expected cubic structure of metals?

I've noticed that some groups of metals with similar properties tend to belong to the same cubic structure group, such as $\text{FCC, BCC, or HCP}$. What is a good explanation as to why these metals ...
5
votes
2answers
50 views

How do people check the type of defect in a crystal?

There are many types of defects like Vacancy Interstitial Schottky Frenkel Non-Stoichiometric Alien Impurities But given a sample, how do scientists know which kind of defect is present in it ...
0
votes
1answer
35 views

What is the length of a unit cell of CuCl assuming that it is fcc?

The density of CuCl is given - x gm/cmm The crystal structure is assumed to be fcc. My teacher is claiming the we can apply the formula $$\rho=\frac{Z * M}{a^3 * N_0}$$ And he took M = 35.5+63.5gm = ...
1
vote
1answer
45 views

Structure of diamond

"diamond structure. Every carbon atom is bonded to four other carbon atoms forming a three-dimensional lattice of chair conformations." SENTENCE FROM A BOOK What does this mean? Where I am struck ...
0
votes
2answers
26 views

What are Lattice Points

What are lattice points exactly? And Also How many Lattice Points are there in each of the Unit Cells?
8
votes
1answer
316 views

What are these crystals on my champagne cork?

I opened up a bottle of champagne that was left in a wine cooler for approx. 8 years. To my astonishment there were small crystals at the underside of the cork. The crystals are colorless, odorless ...
0
votes
1answer
20 views

Crystal structure in function of pressure

If you were to investigate crystal structure changes as a function of pressure, which metals would you study first? Last? Why?
3
votes
1answer
50 views

Elementar cell of Y2O3

I think this picture from wikipedia is wrong because I count: \begin{align} \left. \begin{array}{ccccr} 1&×&1 &= &\ce{1~Y} \\ 6&×&\frac{1}{8} &= &\ce{\frac{3}{4}O} ...
7
votes
1answer
287 views

Is BCl₅ possible?

Is $\ce{BCl5}$ possible? I saw it in book. As far as we can see there is no way to get 5 chlorine atoms with boron.
5
votes
2answers
178 views

If salt crystals make a cube shape, what is this 'X' marking?

I am an amateur, with very little professional chemistry knowledge. I was doing a demonstration / experiment with my 6 year old child. We took very warm normal tap water, and dissolved into it a ...
2
votes
1answer
68 views

Chemical bonding - lattice energy

Question: Why is ionic lattice energy inversely proportional to the radius of the atom? Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, ...
0
votes
0answers
14 views

Polymer Crystallinity

See the following question: I think the answer is A because of the hydrogen bond in the side group, thus the degree of secondary bonding between parallel chain segments is higher. Is my thinking ...
6
votes
1answer
70 views

How does the crystal know where to stop stacking the unit cells?

I tried to make different crystals in the cubic system by stacking cubes in a 3d software. However I need to tell the software where to skip rows or stop stacking the unit cells in a specific ...
1
vote
1answer
41 views

How do we know the size of atoms in body centered cubic system?

I'm told that in the normal cubic system there are $\frac18$ of an atom at each corner and these atoms' radius are such that $a = 2r$ ($a$ is the lattice constant, $r$ radius of an atom). In bbc ...
5
votes
3answers
925 views

Are metallic/ionic bonds weaker than covalent bonds? I was taught the opposite. Now I'm confused

In mineralogy class, I was taught that metallic and ionic bonds are weaker than covalent bonds and that's why quartz and diamond have such a high hardness value. However, in organic chemistry class, I ...
1
vote
1answer
92 views

Why do NaHCO₃ and KHCO₃ have different crystal structures?

Why do $\ce{NaHCO3}$ and $\ce{KHCO3}$ have different crystal structures? We had this in a test today and this got me stumped... My questions are: Do $\ce{NaHCO3}$ and $\ce{KHCO3}$ possess ...
1
vote
1answer
90 views

Bonding, multiplicity and quantum chemistry for FeP$_2$

I'm trying to do some quantum chemical calculations for the linear molecule FeP$_2$ in the gas phase as well as its crystal (orthorhombic symmetry like here). I am lead to believe that in both cases ...
0
votes
0answers
28 views

How to determine mineral properties based on chemical formula?

I need to learn a bunch of minerals and their properties. What I want is some sort of rule which helps me deduce color, crystal system, luster etc. I know that different kind of ions give specific ...
1
vote
1answer
163 views

How to memorize 7 crystal systems?

Is there any trick to memorize the angles and sides of 7 crystal systems of crystalline solids? 1. Cubic 2. Tetragonal 3. Orthorhombic 4. Monoclinic 5. Hexagonal 6. Rhombohedral or Trigonal 7. ...
1
vote
1answer
63 views

What is the minimum distance of Rubidium and Iod ions in a centered cube?

I have a problem to visualize the following assignment: What is the minimum distance between $\ce{Rb^+}$ and $\ce{I^-}$ ions if radius of $\ce{Rb^+}$ is ${1.49\cdot10^{-10}}~\mathrm{m}$ and radius ...
6
votes
3answers
606 views

How many Ga atoms are connected to one As atom in solid state Gallium arsenide

Let's start straight away. In this book on page 4 Gallium arsenide's bond structure is shown like this: $As$ is shown making $5$ covalent bonds. Recently I came across this book. The bond structure ...
1
vote
1answer
119 views

Hexagonal unit cells

I know 3 types of unit cells, the simple cubic, the body centered and the face centered. But what is a hexagonal unit cell, and why does it have a hexagon base while others are all cut into a cubic? ...
2
votes
0answers
60 views

Why is there one octahedral and two tetrahedral positions for every anion in a close packed structure?

I'm reading about ionic crystal structures with planes of close-packed anions and the interstitial sites for cations. There are two types of interstitial sites: tetrahedral and octahedral. That makes ...
1
vote
2answers
201 views

Why are cations ordinarily smaller than anions?

I'm reading on ionic crystal structures and am confused by this from my textbook: Because the metallic elements give up electrons when ionized, cations are ordinarily smaller than anions I ...
3
votes
2answers
234 views

Is a diamond a single molecule?

Assuming a perfect diamond with no impurities. Would this diamond considered to be a single large molecule? Browsing the interweb I found several opinions about this but did not find a clear Yes or ...
1
vote
1answer
217 views

is there any mnemonic for the AXE method?

Is there any mnemonic that helps remembering the names of the different geometries (Shapes) that we obtain from applying the AXE method ?
3
votes
2answers
81 views

Is it possible to cut yourself on pyrite?

I am planning an RPG adventure where the characters might end up getting a large cubic lump of "gold", which in reality, as you might have guessed, is in fact pyrite. I also wanted to plan for the ...
3
votes
3answers
129 views

Why does ZnO turn yellow when it is hot?

Why does ZnO's color become yellow when it is hot? I have read that it is because of physical properties, but I need a more elaborate explanation.
3
votes
1answer
298 views

How do you determine a chemical formula given the molecule's crystal structure?

How do you determine the chemical formula of a compound given its crystal structure?
0
votes
0answers
379 views

How to calculate lattice parameter only using planes and d spacing

I am trying to find lattice parameter of a hexagonal crystal, usually I use cellcalc for calculating lattice parameter of a crystal structure. In that software it asks only two queries, one is details ...
1
vote
1answer
46 views

Rapidly cooling Aluminum vapour to solid state?

What sort of a microstructure would you get on bubbling Aluminium vapors through a large tank of Helium?Would it be a glassy microstructure and/or would you get nano-powders? and/or a new crystal ...
2
votes
0answers
86 views

Bond Lengths in FCC, BCC and HCP Structures

I was wondering what the crystal structures of FCC, BCC and HCP actually look like, and where atoms are placed in their configuration? Specifically I'm looking at elemental nickel, iron and cobalt ...
0
votes
1answer
12k views

What's the difference between alpha-glucose and beta-glucose?

What's the difference between $\alpha$-D-glucose and $\beta$-D-glucose? Are they isoforms? Or do they differ in their elemental composition?
2
votes
3answers
829 views

What's up with SiO2 being tetrahedral?

If silicon dioxide tends to form a crystal lattice with four Os around a central S, why isn't the molecular formula $\ce{SiO4}$ then? I'm confused why it's unique in that its molecular formula doesn't ...
0
votes
1answer
133 views

Wasn't Rutherford's assumption of gold foil to be made of single layer wrong?

My teacher taught about Rutherford's gold foil experiment today. Sir said that, Rutherford used gold foil of thickness $10^{-7}$ m and concluded atom to be of size $10^{-10}$ m. Sir also said that ...