All Questions
Tagged with lattices crystal-structure
30 questions
-1
votes
1
answer
60
views
If AlCl3 has such a high lattice energy, why is it so soluble in organic solvents?
AlCl3 is well known to be relatively covalent, but doesn't solubility generally go down as lattice energy increases, (I.e born-haber cycle?)? However it's soluble in many organic solvents
- 105
2
votes
0
answers
41
views
What is the precise definition of crystal systems and unit cell?
I was just wondering why there wasn't a rhombic 2D Bravais unit cell (wasn't there in the material provided to us) and realised upon drawing that it is the same as a centered rectangular unit cell. ...
- 21
4
votes
1
answer
777
views
Why does KCl have FCC structure instead of BCC?
I have this table here.
\begin{array} {|r|r|}\hline \text{Radius Ratio} & \text{Coordination number} & \text{Type of Void} \\ \hline <0.155 & 2 & \text{Linear} \\ \hline 0.155-0....
-2
votes
2
answers
540
views
What is the difference between alloying and doping? [closed]
When compared to doping, how is alloying different? What modifications to the structure are brought about by both of these?
0
votes
0
answers
61
views
Data for Madelung Constants
Where can I find data for the Madelung constants for various ionic compounds? Specifically, I am looking at silicon tetrachloride, yttrium (III) chloride, zirconium (IV) oxynitrate hydrate, niobium (V)...
3
votes
1
answer
183
views
How do other elements fit into a diamond's carbon lattice (e.g. nitrogen in yellow diamonds)
Traditional pure-carbon diamonds have a simple structure (tetrahedral, if I'm not mistaken). But common types of diamonds have other elements within them. For example, yellow diamond has nitrogen in ...
- 131
-2
votes
1
answer
2k
views
In calculating the radius ratio in a tetrahedral site in an FCC lattice, why do we take tetrahedral void in the middle of the body diagonal line? [closed]
When calculating the ratio of cation / the ratio of anion in a Tetrahedral system in an FCC lattice, why do we take the void to be in the center instead of it being √3a/4 from the corner.
-1
votes
2
answers
151
views
Why does density decrease when pressure is increased on an NaCl type lattice?
I was told that the effect of pressure on an NaCl type structure would make the atoms come closer and therefore change the type to CsCl type making Z (no of atoms per unit cell) go down, hence density ...
- 19
1
vote
1
answer
5k
views
Radius ratio of octahedral interstitial site in BCC lithium
Problem
Determine the minimum radius of an atom that will just fit into (a) the tetrahedral interstitial site in FCC nickel and (b) the octahedral interstitial site in BCC lithium.
Solution
(a) For ...
- 284
1
vote
0
answers
37
views
HCP and hexagonal primitive cell [duplicate]
There are 14 types of Bravais lattices one of them is hexagonal which is just present as primitive cell ie the basis are at its corners , now when I read about hexagonal closed packing I came to know ...
- 29
3
votes
1
answer
1k
views
Whats the difference between unit cell and motif?
The definition in my material is that motif and unit cells are both a repeating unit, but whereas motif is with respect to 2D lattice the unit cell is with respect to 3D lattice. But I can't find ...
- 230
8
votes
2
answers
7k
views
Why are there exactly 5 types of two-dimensional lattices, and what distinguishes them?
In the book Chemistry: The Central Science, they introduced the following 5 types of two-dimensional lattices:
The book said that the blue square represents the unit cell, the black dots are lattice ...
- 107
0
votes
1
answer
319
views
Height of CCP Lattice
Are the height of the Cubic Close packing Lattice and the cubic Hexagonal Close Packing the same?
My understanding says that these unit cells are formed by different arrangement of atoms, ABC for CCP ...
4
votes
1
answer
6k
views
Finding the atomic packing factor (APF) of Sodium Chloride and other FCC ionic compounds
For a piece of coursework I am doing, I need to calculate the atomic packing factor of some ionic compounds. I have had no formal teaching in this area, so what I know comes from information I have ...
- 41
2
votes
1
answer
331
views
If a good choice of a unit cell should be the one of most symmetry ,then why keep body centered tetragonal if face centered cubic exists?
For any lattice a good choice of a unit cell is the one that is the most symmetric.
Now if every lattice made by a body centered tetragonal unit cell can be made by a face centered cubic unit cell ,...
- 313
2
votes
2
answers
2k
views
Conventional unit cell for a hexagonal crystal system
The figure shows a unit cell of a hexagonal crystal system. Drawn in bold, is the unit cell. The lightly shaded one is a unit cell as well and has a six fold symmetry along an axis, hence is more ...
- 313
1
vote
1
answer
269
views
Interplanar distance given Miller indice of the planes
Say we've a cubic crystal of unity edge length.
A set of planes in such a crystal is specified by their miller indice as $(3 2 0)$. One of these planes then has intercepts on the axes as $(2 ,3 ,\...
- 313
1
vote
1
answer
2k
views
How do I find miller indices for a plane whose intercepts are fractions of the lattice constant?
[I'm talking with respect to cubic lattices alone.]
For instance, if a plane has $x,y,z$ intercepts $a/2,a/2,a/2$ (where $a$ is the lattice constant) the miller index would be $[2\space2\space2]$. The ...
- 113
6
votes
3
answers
10k
views
Converting fractional coordinates into cartesian coordinates for crystallography
So let's say for a given molecule I have the volume of a unit cell, the shape of the unit cell (monoclinic, cubic, etc), the cell angles alpha, beta, and gamma, the cell lengths a,b, and c, and a list ...
0
votes
0
answers
125
views
What is meant by "rotation about an axis that passes through a lattice point"?
I am currently studying Introduction to Solid State Physics, 8th edition, by Charles Kittel. In the section Fundamental Types of Lattices of chapter 1, the author says the following:
Crystal lattices ...
- 1,103
0
votes
2
answers
979
views
Sketching lattice points, primitive axes, primitive cell, and basis of atoms
I am currently studying Introduction to Solid State Physics, 8th edition, by Kittel. Chapter 1 provides the following figure and accompanying explanations:
It also says the following:
An ideal ...
- 1,103
5
votes
0
answers
173
views
How is the Born-Lande equation modified when the structure is not NaCl?
Often the Born-Lande equation is quoted (alongwith the calculation of the Madelung constant and Born exponent) with reference to rock-salt structure. But what if we take some other crystal, like ...
- 405
-1
votes
2
answers
2k
views
How many nearest neighbours does a corner atom have? [closed]
Figure shows a unit cell of a cubic lattice. The atom in the middle has 8 nearest neighbours (the atoms in the corner). How many nearest neighbours does a corner atom has ?
I identified the given ...
- 123
2
votes
1
answer
600
views
Unit cell structure of ionic crystal
I have a question about the structure of an LiH unit cell, and while this is related to a homework problem, it isn't the problem itself, I'm just looking for conceptual understanding. I've already ...
- 29
6
votes
2
answers
1k
views
Stacking two square (2D) layers to make a 3D close packed structure
My textbook states these ways of stacking 2D layers to make 3D close packed structures:
Square close packing layer over Square close packing layer (though not written explicitly, the illustration ...
- 261
1
vote
1
answer
866
views
Does a unit cell have to contain a whole number of atoms?
I was given this problem recently to compute the number of ions in a unit cell of ferrous oxide $\ce{FeO}$. The data given was:
Side length $a = \pu{5 Å}$
Density $d = \pu{4 g/cc}$
Using the formula ...
- 6,338
-1
votes
1
answer
170
views
Lattice energy while bond formation [closed]
My chemistry lecturer taught us that lattice energy is the energy required to break an ionic bond between two oppositely charged ions in a crystal lattice.
He then told us that lattice energy is ...
- 175
1
vote
0
answers
113
views
Difference in properties of water as ligand vs 'in lattice'
I'm trying to understand the difference in properties between water in crystals in different positions in the lattice. In this wikipedia article It quotes:
Both notations can be combined as for ...
- 111
-2
votes
1
answer
68
views
Electrical resistivity [closed]
I have read that in non-metals solids the electric resistivity is reduced if we increase temperature.But this isn't logical.I mean if temperature is increased ok the electrons get extra energy but as ...
- 21
2
votes
1
answer
71
views
Is this approach to finding density in crystal lattice acceptable?
In answering a question in an elementary chemistry text that asks for the density of gold ($\ce{Au}$) based on crystal dimensions and weight per atom, I found the approach I used was a little ...
- 994